View Full Version : AR- Piston or Direct Impingement?
The question still comes up and the debate rages on- “Should I Get a Piston for my AR or Direct Impingement?” The answer is, the AR already has a piston and none use a direct impingement system.
First, let's take a look at a conventional Direct Impingement system. The key feature is that gases act directly on carrier. The gas travels through a gas tube to act directly on the carrier. The following diagrams show the DI system of the Ljungman Ag m/42.
http://www.gotavapen.se/gota/artiklar/ag42/ag42_601det.jpg
http://www.gotavapen.se/gota/artiklar/ag42/ag42_301det.jpg
Eugene Stoner said in the original patent for his gas sytem “This invention is a true expanding gas system instead of the conventional impinging gas system.” The gases enter the expansion chamber inside the bolt carrier and drives the carrier rearward. The piston is actually the tail piece of the bolt. The rearward motion continues, unlocking the bolt and extracting the spent case.
The system is designed to be self regulating. When enough pressure enters to operate the action and the carrier begins to move, the key separates from the tube and cuts off the gas flow to the carrier. There are also vents in the carrier to allow the gases to escape and the pressure to drop inside the cylinder when the piston seals move past them. After that, the action is powered by momentum and returned into position by the energy stored in the action spring.
http://i115.photobucket.com/albums/n289/SgtSongDog/Research/ARGasSystemDrawing.jpg
In the AR system, Eugene Stoner eliminated the actuator rod of other piston gas systems and incorporates the piston with the bolt and the cylinder with the bolt carrier to “...provide smoother operation and longer life of the working parts...” The patent goes on to explain that since all the actuating force is inline with the bore and bolt to the shooter's shoulder “all of the off center loads found in most other types of gas actuated weapons are eliminated” to cut down on “climb” during automatic fire.
The so-called “piston upper” (ie- Adams, HK416, LWRC etc.,) does not convert an AR from direct impingement system to a piston system. It converts the AR from an inline piston system to an offset piston system and adds an actuator rod.
Anyone tells you your AR needs a piston to run cleaner/cooler/tacticooler, tell them
http://i115.photobucket.com/albums/n289/SgtSongDog/AR%20Carbine/DSC_0013.jpg
"No thank you. My AR already has a piston"
Stoner Patent #2,951,424: http://www.google.com/patents?id=ETJjAAAAEBAJ&printsec=abstract&zoom=4#v=onepage&q&f=false
Note: I will edit this post as my research continues, to correct any mistakes and for clarity
sinlessorrow
02-12-12, 00:00
excellent write up
i gotta say stoner was a genius, its no wonder his system is still in use today as one of the best rifles in the world
pilotguyo540
02-12-12, 00:25
Well said. I hope this gets stickied.
N8rfastback
02-12-12, 10:06
Awesome explanation. That puts things into perspective.
Sent from my A500 using Tapatalk
TacMedic556
02-12-12, 10:15
CAN WE GET A HALLELUJAH!
Right on. Excellent write up. Thanks.
infidelprodigy
02-12-12, 10:48
Excellent explanation of the inner workings. Hard for detractors to argue with what Stoner wrote in the patent paperwork........
It's always nice to pick up more info on the firearm we love so much, great write-up. Strap up for all the naysayers' comments...they're sure to come. :rolleyes:
Suwannee Tim
02-13-12, 08:37
I've always thought the name "Direct Impingement" was unfortunate. A more descriptive name would contain the word "coaxial" as this is the feature that truly distinguishes this system from all the others. Perhaps "coaxial piston" or "coaxial system" or some such. It is indeed true that all ARs, indeed, all centerfire auto rifles except the handful of recoil operated systems, are piston systems.
Excelent post.
There was a post on TOS about this also, I believe by Steve from adco. (there are 2 "bigbore"s over there so im not sure which one wrote this). It has cut-section pictures to help people see what actually is going on.
http://www.ar15.com/content/page.html?id=535
Im assuming we can link there. If not, mods, just remove link and I'll pick up what you're throwing down.;)
DeltaSierra
02-13-12, 17:23
Mistwolf -
Great post. Thanks for taking the time to write this up.....
I've always thought the name "Direct Impingement" was unfortunate. A more descriptive name would contain the word "coaxial" as this is the feature that truly distinguishes this system from all the others. Perhaps "coaxial piston" or "coaxial system" or some such. It is indeed true that all ARs, indeed, all centerfire auto rifles except the handful of recoil operated systems, are piston systems.
Well, the term "coaxial" implies that the axes of two components (in this case the barrel and the piston) are parallel, but not necessarily that the axes are the same. I think a better description of the Stoner system is just "axial" or, even better, "in-line."
The actual patent is a great read. In the description, Mr. Stoner states: "This invention is a true expanding gas system instead of the conventional impinging gas system."
In light of this, I will never again refer to my 6920 as a direct-impingement weapon.
Great info, MistWolf! Thank you!
~Dan
mikeshin1023
02-13-12, 19:37
Pretty sure "coaxial" means the same axis.
From Dictionary.com:
"Also, co·ax·al [koh-ak-suhl] Show IPA. having a common axis or coincident axes."
An Undocumented Worker
02-13-12, 19:41
Well, the term "coaxial" implies that the axes of two components (in this case the barrel and the piston) are parallel, but not necessarily that the axes are the same. I think a better description of the Stoner system is just "axial" or, even better, "in-line."
The actual patent is a great read. In the description, Mr. Stoner states: "This invention is a true expanding gas system instead of the conventional impinging gas system."
In light of this, I will never again refer to my 6920 as a direct-impingement weapon.
Great info, MistWolf! Thank you!
~Dan
coaxial [kəʊˈæksɪəl], coaxal [kəʊˈæksəl]
adj
1. (Mathematics) having or being mounted on a common axis
2. (Mathematics) Geometry (of a set of circles) having all the centres on a straight line
3. (Electronics) Electronics formed from, using, or connected to a coaxial cable
Pretty sure Coaxial is the correct term.
Ok...but I still like the sound of "in-line piston system" better. Has a nice ring to it and sounds kind of poetic... :D
The salient point is that the Stoner system is not "direct impingement"...
~Dan
More precisely, it says "This invention is a true expanding gas system instead of the conventional impinging gas system."
It doesn't matter if the AR is a direct impingement system or not. The point being is it does have a piston (and I suppose push come to shove, so does the conventional DI system) and that the offset piston upper adds an actuator rod and introduces off center recoil.
Critics of the AR inline system talk about tight tolerances. Yet the carrier has little contact with the upper receiver. The tight tolerances are between the bolt and the carrier.
Perhaps someone with more experience with the AR can tell us where most of the crud and debris collects in the AR and what the direct effects are. I read statements that carbon build up on the tail cone of the piston doesn't matter. I can see where debris in the barrel extension would prevent the bolt from locking up properly. I also know that keeping the action lubed will keep it running.
The offset piston system can produce tough and reliable rifles. After the AR, Eugene Stoner went on to engineer other weapons using offset pistons. But his design that went on to be successful is the inline piston of the AR
sinlessorrow
02-14-12, 14:33
The ar as we know it is also tough and reliable.
Also carbon buildup doesnt make a diff unless its in excess, like 5000 rounds. In the military you wont even come close to that before cleaning. A combat load is generally 7 magazines.
Wipin down the ar-15 once a day and lubin will keep it running
The ar as we know it is also tough and reliable...
I didn't mean to imply the AR isn't. I read reports from the first Gulf War that the AR proved to be the most reliable of the 5.56 NATO rifles that saw action. One advantage the AR has is that it's spent more time in the crucible of combat in the harshest of conditions than almost any other rifle
Also carbon buildup doesnt make a diff unless its in excess, like 5000 rounds. In the military you wont even come close to that before cleaning. A combat load is generally 7 magazines.
Carbon buildup is not the only issue for mil guys.
Sand from weapons being exposed to the elements, dirt and vegetation getting into the action or getting on the mags in the pouches. Snow and ice getting into the action.
I had a guy whose weapon malfunctioned during a live fire ex, squad hasty attack. Bolt wouldn't cycle, and we couldn't lock the bolt to the rear. It was stuck, barely out of battery. With a leatherman and some brute force, we finally managed to get the bolt free.
Upon inspection of the barrel extension and inside the reciver, we saw small pebbles, the size of coarsly grated pepper. They locked the action up.
During one operation a team had several guns fail to function after a while, during contact; HK416's, MG-3's and M2 .50 cals due to mud and dirt getting EVERYWHERE.
Lubing helps, but only to a certain point.
sinlessorrow
02-14-12, 15:24
Carbon buildup is not the only issue for mil guys.
Sand from weapons being exposed to the elements, dirt and vegetation getting into the action or getting on the mags in the pouches. Snow and ice getting into the action.
I had a guy whose weapon malfunctioned during a live fire ex, squad hasty attack. Bolt wouldn't cycle, and we couldn't lock the bolt to the rear. It was stuck, barely out of battery. With a leatherman and some brute force, we finally managed to get the bolt free.
Upon inspection of the barrel extension and inside the reciver, we saw small pebbles, the size of coarsly grated pepper. They locked the action up.
During one operation a team had several guns fail to function after a while, during contact; HK416's, MG-3's and M2 .50 cals due to mud and dirt getting EVERYWHERE.
Lubing helps, but only to a certain point.
Certainly there are other things, i was just stating the carbon buildup from the stoner system is a non issue.
People make it out likes its a plague that kills the rifle but its not an issue if its cleanedduring downtime.
Eta: my comment was not aimed at anyone just a general comment
Why do most modern assault rifles utilize short stroke (op rod) or long stroke (AK style) rather than the Stoner type piston?
Actually, do any new weapons not of the Ar 15 fow utilize it? Might there be a reason for this? I'm just asking as I don't know.
But his design that went on to be successful is the inline piston of the AR
The design of Stoner has the bolt carrier housing doing the work, as a moving
cylinder. The bolt (piston) is initially stationary. The bolt in Stoner’s design
doesn’t make the same comparison to the actuating rod (piston) in a gas-piston
system, which does move and influences the action of the bolt carrier group.
If the actuating rod were attached to the bolt carrier housing, then this could still
be considered an expanding gas system, for how else would the actuating rod move.
The design of Stoner has the bolt carrier housing doing the work, as a moving
cylinder. The bolt (piston) is initially stationary.
That was well established in the first post of this thread
The bolt in Stoner’s design doesn’t make the same comparison to the actuating rod (piston) in a gas-piston system, which does move and influences the action of the bolt carrier group.
I do not understand what you're trying to say here. Using an actuating rod, either as part of the piston or as a separate part, necessitates it being place offset to the bore and bolt. By eliminating the actuator rod and integrating the piston with the bolt, it brings all the recoil forces inline with the bore and to reduce muzzle rise
If the actuating rod were attached to the bolt carrier housing, then this could still be considered an expanding gas system, for how else would the actuating rod move.
Eugene Stoner didn't see it this way as he describes his system as being an expanding gas system in the original patent. I believe what makes a system an expanding gas system is the fact that the gas uses a chamber that expands in volume as the gas pressurizes it. The AR cylinder inside the carrier is such a chamber. (Note that the AR piston remains inside the cylinder unlike the Ljungman.) Whether a system uses an actuator rod or not has nothing to do with it
Freedoooom
02-14-12, 17:03
Whole lot of crazy.
You have essentially for an example argued that coal turbine actually is just the same exact thing as a hydroelectric turbine and anyone who tells you coal turbine runs hotter is just crazy.
No its not. They completely two different principles of how to cycle a gun. One uses the forces of hot gasses inside the chamber, one uses it under a hand guard to push a rod.
There is no debate whether a piston system runs cleaner and cooler. Its just a fact, of physics and empirical evidence. Your own post even points to this, it not only blows hot gas into a key, it blows it into the bolt it self, which also blows gas out through out the whole chamber.
SpaceWrangler
02-14-12, 17:21
I'm pretty sure you'll find it doesn't blow gas into the chamber.
Whole lot of crazy.
You have essentially for an example argued that coal turbine actually is just the same exact thing as a hydroelectric turbine and anyone who tells you coal turbine runs hotter is just crazy.
No its not. They completely two different principles of how to cycle a gun. One uses the forces of hot gasses inside the chamber, one uses it under a hand guard to push a rod.
There is no debate whether a piston system runs cleaner and cooler. Its just a fact, of physics and empirical evidence. Your own post even points to this, it not only blows hot gas into a key, it blows it into the bolt it self, which also blows gas out through out the whole chamber.
From what I understand the gas port on DI guns will expand and wear due to the backup of pressure at that point, whereas with the piston system, it reduces the back pressure more quickly and helps save the port- but the return argument is this- who is going to shoot that many rounds- some people have and why not just admit we don't drive model T's anymore and there are many improvements in all aspects of weaponry- you know GS might have taken a likin to the piston but his heart wore out- Thanks, CB
Whole lot of crazy.
You have essentially for an example argued that coal turbine actually is just the same exact thing as a hydroelectric turbine and anyone who tells you coal turbine runs hotter is just crazy.
No its not. They completely two different principles of how to cycle a gun. One uses the forces of hot gasses inside the chamber, one uses it under a hand guard to push a rod.
There is no debate whether a piston system runs cleaner and cooler. Its just a fact, of physics and empirical evidence. Your own post even points to this, it not only blows hot gas into a key, it blows it into the bolt it self, which also blows gas out through out the whole chamber.
I see what you're trying to say. However, there are assumptions behind your premise. You are assuming their is significant difference in heat between the inline system and the offset system. What are the actual temperature differences of the BCG when shooting 200 rounds of ammo in an offset upper compared to an inline upper? How many BTUs of heat are actually carried into the expansion chamber of the carrier with each shot? How much hotter does the gas block of an offset piston upper get compared to the inline piston upper? Does that extra heat contribute to port erosion? Does it add to barrel heat? Will it make the handguards hotter affecting shooter's ability to handle the rifle? How much carbon build up can the piston and cylinder of the offset upper take before it impacts function?
Where is the empirical data? Show me the physics. I'm still searching for these answers.
Also, you may want to re-think your example. While the coal turbine and hydroelectric turbine both generate electricity, they are different technologies utilizing completely different power sources
Battle*Hound
02-14-12, 17:55
LMT MRP Piston Uppers = YUMMM
jonconsiglio
02-14-12, 18:27
SNIP
LMT has a piston system because they sell and customers were asking, not because they think it's necessary. I think it's pretty obvious why Colt has a piston coming.
I have two SCARs that see a lot of use. I've owned a couple piston ARs but prefer DI and currently run all DI ARs. I've used them in all typed of environments and pushed them very hard, gotten them filthy and ran all types of ammo. The piston does nothing truly better than my ARs unless we're talking SBRs (on the extreme end) or suppressed full auto fire. For most all normal use, including military use, the AR with it's DI system is perfectly acceptable.
As to why other rifles aren't using it, I have no idea. I just know what works. I'm all for advancements in the industry if they are truly better. If they're just a different way of doing things at an increased cost with very little benefit, I don't see it as a great idea or worth the extra cost.
Just a quick observation regarding specific tolerances of the M4/M16 FOW when it comes to fouling, since reliability came up.
When browsing the MIL-SPEC for the M193 and M855, they have a requirement they need to pass in regards to fouling:
M193 (MIL-C9963 F):
3.12 Fouling. -The fouling accumulated In the weapon during the firing of 1000 sample cartridges shall not cause failure of the weapon to function.
http://www.everyspec.com/MIL-SPECS/MIL+SPECS+(MIL-C)/MIL-C-9963F_25766/
M855 (MIL-C-63989A):
3.13 Fouling. The fouling accumulated in the M16A2 and M249 weapons during the firinq of the sample cartridges shall not cause failure of either weapon to function
NOTE 4 The sample for this test shall be the sample
specified for the Function and Casualty test for each respective
weapon, i.e. 800 rounds for the M249 and 800 rounds for the M16A2.
http://www.everyspec.com/MIL-SPECS/MIL+SPECS+(MIL-C)/MIL-C-63989A_37914/
Now, these spec's indicate that the weapon should function firing 4-5 times the normal combat load without failure, with these loads. It does not say anything about the lubing scheme used for the testing.
According to the MIL-DTL-71186A for the M4A1 Carbine, the Endurance test is 6000 rounds, and having to pass these requirements:
3.6.7 Endurance.
3.6.7.1 Endurance functioning. The weapon shall fire 6,000 rounds of M855, 5.56mm ball cartridge in accordance with drawing 9342868. There shall be no more than the number of malfunctions and unserviceable parts allowed in Table I.
Table I:
http://img692.imageshack.us/img692/9937/table1q.png
4.5.7.1 Endurance functioning. Each weapon shall be fired in accordance with the Operator’s Manual 9-1005-319-10 and shall be held in a firing stand simulating shoulder firing in accordance with drawing 11837945 (auto firing), using ammunition M855, 5.56mm ball cartridges in accordance with drawing 9342868.
a. Firing procedure. Firing shall be accomplished in 50 cycles using 30
round magazines. One (1) firing cycle shall be as specified in Table V.
Cooling of the barrel shall be to the point that it is capable of being held by the bare hand. Supplemental cooling is permissible in the hand guard area.
http://img717.imageshack.us/img717/6344/tablevt.png
b. Cleaning and lubrication. Weapons shall be cleaned and lubricated at the beginning of the test and at the end of every 10 cycles. Weapons shall be lubricated after the fifth cycle and at every 10 cycle increment. No other cleaning and lubrication shall be performed during this test. At the close of each day's firing, the weapon shall be protected against corrosion.
i. Lubrication. Weapons shall have been lubricated using lubricant
in accordance with MIL-PRF-63460. Apply a light coat of oil to
all surfaces of the bolt carrier group. (Do not apply excessive oil
in the bolt firing pin recess.) Apply a moderate coat of oil on all
firing mechanism components in lower receiver.
http://www.everyspec.com/MIL-SPECS/MIL+SPECS+(MIL-DTL)/MIL-DTL-71186A_30742/
It is quite clear that the tolerance levels are quite good, in my opinion. I do not understand why there has to be so much contention between DI and Short Stroke Piston systems.
If your weapon and ammunition combination can pass the requirements documented in the mil-spec's provided here, I would say that all is well. M855 must not cause a failure to function in 800 rounds (M16A2). That is 2/3 of total rounds fired in the course of 10 firing cycles fired before relube and cleaning.
I tried searching, but could not find the equivalent document for the HK416 (Short Stroke Piston). Probably because it is SOF issue, thus not being publicly available. Therefore I cannot say if testing requirements are the same or more rigorous.
Like I said, if your weapon can pass the specs shown in my reply, you are probably good to go.
Thomas M-4
02-14-12, 20:19
[QUOTE=Koshinn;1230447 Why didn't HK utilize it in the XM8? Or FN with the SCAR? QUOTE]
Those are techincaly called gas tappet systems. They differ from conventional short stroke operating systems the piston is contained in the gas block and there is not a sperate operating rod its actully part of the BCG.
Crow Hunter
02-14-12, 20:20
As to why other companies haven't used "DI" in their designs.
I think you will find that most manufacturers go with what they know and have experience with.
I don't know this as a 100% fact (just pictures) but I would imagine if you look at the designs of the HK416/G36/XM8/L85 you will find very similar gas pistons setups/designs. Not just principle actually dimensionally similar.
Same way with the FN guns or AK rifles. In my experience once engineers within a company find something that works, they tend to build on this design with minor variations/improvements.
Trying to design a rifle even using open source prints without the testing or development background is just asking for problems.
In my experience, the AK bolt/BCG is dirtier than the AR after firing the same number of rounds.:p
Let's steer this thread back on to it's original course.
1) The AR uses a piston and cylinder.
2) The AR does not use an actuator rod.
3) The piston is centerline with the bolt to eliminate offset recoil.
4) Eugene Stoner wrote in the patent that this system is not a conventional direct impingement system.
Please keep the discussion at a professional level.
Arctic, thank you for providing documentation to support your post
I think most countries have always been piston so developed the same thpe of piston.
Germans, Norway, Sweden, Spain, Turkey et. used rolled delayed blow back. France uses delayed blow back as well. Pistons actually dominated other side of Steel Curtain. Of course there was FN FAL and several AK-inspired designs on the West as well. Actually G3 has as long users list as FN FAL, so hard to say which system dominated, but saying that most countries (regarding "free world") were been piston is probably not founded.
Most countries in my area adopted AR-15 design only for SOF use, due to great ergonomy and flexibility of configuration. Fact that SOF units can provide extended maintenance for those "race rifles" and usually in SOF use fire exchange is short (or so they believed before Iraq and A-Stan). In time some of those units migrated to HK416. But for equipping whole armies M4 or M16 were considered too fragile and troublesome for regular soldiers (also dependence of US policy is worth mentioning as drawback on adopting those systems). Good example is Czech Republic - that after initial love to M4, when they SOF started to use them, later they decided that regular soldiers require something more solid and got back to design CZ 805 Bren. Also, even in SOF, when there is water included, units tend to stay away from AR designs (even with HK416 OTB capability) look elsewhere (G36 seem to be popular choice for eg, Norway, Poland)
I tried searching, but could not find the equivalent document for the HK416 (Short Stroke Piston). Probably because it is SOF issue, thus not being publicly available. Therefore I cannot say if testing requirements are the same or more rigorous.
Per G3Kurz (former HK USA employee involved in HK416 project):
In tests at HK for Lot Acceptance of the first batch of HK416's going to the first customer the HK416 10" fired >15,000 rounds w/o a single stoppage and no parts failures (that same gun was later shot by HK beyond 25,000 with the same results AND the gun after the 15,000 rounds still printed sub-1" 5-shot groups at 100 meters from a fixture using 55 grain IMI match ammo)
http://www.hkpro.com/forum/hk-talk/135557-dust-test.html#post1001985
BTW Polish acceptance test (heritage of Warsaw Pact rules) ask to test rifle by shooting one round with barrel obscured by sand at muzzle end. Test is passed if rifle does not fail in way that makes pieces separate from rifle nor any danger to soldier arise (further function is not required).G36, HK416, Beryl or UKM-2000 passes this acceptance requirement. Do not know if M4 or M16 are tested this way, but their sensibility to barrel obstructions can be reason some military forces look somewhere else.
I don't know this as a 100% fact (just pictures) but I would imagine if you look at the designs of the HK416/G36/XM8/L85 you will find very similar gas pistons setups/designs. Not just principle actually dimensionally similar.
No wonder. L85 takes a lot from AR18 (yes, mr Stoner again), that was supposed to be improvement over AR15. HK were upgrading L85 for Brits, HK designed G36 and XM8. And HK were upgrading M4 for US SOF (this is how HK416 started). No wonder design is similar - it works, so why change it. Actually HK416 piston itself is same part as in G36.
In my experience, the AK bolt/BCG is dirtier than the AR after firing the same number of rounds.:p
And what ammo with how clean powder you use in AK and what in AR? When I use same ammo in my piston AR (HK) and AK (Mini Beryl 5.56 NATO) I have bolt and BCG in same state dirt wise. With use of RUAG or Hornady, there is virtually nothing to clean in both rifles. With Russian ammo both are very dirty, but not as dirty as my "DI" AR (Stag) was with same ammo. All rifles non-suppressed.
Bottom line. Neither designs of Stoner in line piston, op-rod piston or long stroke piston has only strong sides. Every one of them have some "features" that makes well suited for one task and less suited to other. Stoner AR15 design was made for "fouling less ammunition", that actually never was made. One of design assumptions that allowed to root hot gasses back inside receiver and bolt carrier, was that special ammo with special "ultra clean" powder will be used. This design made AR15 to be "race car" of all assault rifles. But like any race car it needs higher level of attention to run and is more sensitive to where we take it than, lets say, F150. Other armed forces decided to settle for lower accuracy potential and lesser ease of use in exchange of better durability and reliability. For some it is just financial decision of long run costs of using weapon system that requires more maintenance that one that required less. This was never the case for US. Adding external piston in place to internal one into AR15 design is an attempt to gain some of features of other systems into envelope of accuracy and ease of use (and configuration flexibility) of AR15 design. As there is no free lunches, changing operating system has some costs, like, for example higher mass.
Personally I own HK but if I could have KAC (US ITAR will not allow for that) I would not think twice. Two best rifles of both AR worlds for me.
well put Montrala, nothing is perfect unless you believe the hype. the U.S. looks at Stoner and the DI system is godly, it is a very good light/reliable system that many of our soldiers have fought hard with. Stoner did many other designs and Sullivan is still alive. You can follow their work through their lives and see what types of systems they developed.
sinlessorrow
02-15-12, 10:49
well put Montrala, nothing is perfect unless you believe the hype. the U.S. looks at Stoner and the DI system is godly, it is a very good light/reliable system that many of our soldiers have fought hard with. Stoner did many other designs and Sullivan is still alive. You can follow their work through their lives and see what types of systems they developed.
No rifle is godly.
The stoner system is also far more reliable than most give credit for, its far from fragile even in harsh environments. Like i said go look at the OEF, and OIF thread up top and youll have 6 pages of memebers who never had a single stoppage.
Its not a perfect system but none are, but the stoner design is a good combat rifle that has served out military well and will continue to do so until something revolutionary comes out.
I do agree with montrala that depending on one country for parts for uour armies rifles would be a hassle but the stoner system certainly isnt fragile like he mentions
Closing this for a moment to clean it up....
The guy who publicly blamed his iPhone for his mispellings tipped the balance in favor of a scrub...
...once I regained consciousness from the fainting spell my brain induced for its own protection, like an intellectual side-impact airbag.
Yeah, dude, phones cause mispellings....:rolleyes: You know who you are.
EDIT: Re-opened, now with less "less-filling/tastes great", needless name-calling, and the mistaken placement of personal responsibility upon inanimate personal electronic devices....
I would like to take a moment to debunk this "fact".
Empirical evidence? Here you go:
https://www.m4carbine.net/showthread.php?t=57400&highlight=sr556c
https://www.m4carbine.net/showthread.php?t=51218
Furthermore, the temperatures reached as a result of the M4's sustained rate of fire are not enough to be a detriment to the bolt. The critical temperature, the temperature at which any heat treating effects are reversed, for an average steel is 1300 degrees F.
Cleaner? What exactly does that mean? Stoichiometrically, the ratio of powder to byproduct (carbon, gasses, etc) is a fixed number for a given load. I.E. one round of M855 produces the same mass of byproduct in a DI coaxial system as it does in a conventional piston system. The issue to be argued is where that byproduct goes. The belief that carbon fouling will have an adverse effect on the tolerances of a DI piston system but not a typical piston system is irrational as the two systems are functionally the same.
There is no debate whether a piston system runs cleaner and cooler. Its just a fact, of physics and empirical evidence. Your own post even points to this, it not only blows hot gas into a key, it blows it into the bolt it self, which also blows gas out through out the whole chamber.
JSantoro, thank you very much for taking time from your busy day to straighten up this thread. It is deeply appreciated
...Stoner AR15 design was made for "fouling less ammunition", that actually never was made. One of design assumptions that allowed to root hot gasses back inside receiver and bolt carrier, was that special ammo with special "ultra clean" powder will be used...
This is incorrect. The powder Eugene Stoner designed the AR around was a cannon powder in use since WWII. I don't recall exactly which powder it was but it was similar to IMR4895. This family of powders is what they call "log" powder and looks like very short bits of skinny hollow pencil lead. Burn rate is controlled by surface area determined by the external and internal diameters and log length.
The powder they switched to, for what ever reason, was a Winchester spherical (or "ball") powder. Spherical powder is shaped into tiny spheres which may be partially flattened. Burn rate is controlled partially by size and partially by a surface coating of flame retardant, usually graphite. Flame retardant coatings are critical in making ball powders. While it's shape makes ball powder is easier to meter (some Winchester ball powders are designed to be measured by volume rather than weight) the coatings leave behind a gummy residue when burned. Winchester 741 for many years had the reputation of being one of the worse offenders. This change in powders was decided by McNamara, the Secretary of Defense at the time without prior testing or consulting with Stoner. It was also done just prior to ordering the general issue of the M16.
Ironically, shooters often use ball powders when reloading the 5.56 for their ARs because it meters more accurately from a powder throw than log powders.
Another factor that comes into play is that somewhere along the line, somebody decided to sell the new rifle as "self cleaning" and it was issued with no cleaning gear or instructions. While the gummy powder residue from the ball powders alone would not have been an issue, combined with the inability of the troops to perform the most routine of maintenance, deletion of the chrome lined bore and the harsh environment of the jungles of Vietnam, the M16 was doomed to fail from the start.
In reality, the reputation of the M16 for poor reliability stems from political finger pointing to avoid having to take responsibility for poor choices rather than any design flaw. I grew up being told that the original tolerances of the M16 were loosened up for better functioning. Yet, from what I understand, you can take a bolt and carrier made today and use it in an original M16 and vice-versa. (If this is wrong, please correct me). The basic action design remains intact
sinlessorrow
02-15-12, 16:19
JSantoro, thank you very much for taking time from your busy day to straighten up this thread. It is deeply appreciated
This is incorrect. The powder Eugene Stoner designed the AR around was a cannon powder in use since WWII. I don't recall exactly which powder it was but it was similar to IMR4895. This family of powders is what they call "log" powder and looks like very short bits of skinny hollow pencil lead. Burn rate is controlled by surface area determined by the external and internal diameters and log length.
The powder they switched to, for what ever reason, was a Winchester spherical (or "ball") powder. Spherical powder is shaped into tiny spheres which may be partially flattened. Burn rate is controlled partially by size and partially by a surface coating of flame retardant, usually graphite. Flame retardant coatings are critical in making ball powders. While it's shape makes ball powder is easier to meter (some Winchester ball powders are designed to be measured by volume rather than weight) the coatings leave behind a gummy residue when burned. Winchester 741 for many years had the reputation of being one of the worse offenders. This change in powders was decided by McNamara, the Secretary of Defense at the time without prior testing or consulting with Stoner. It was also done just prior to ordering the general issue of the M16.
Ironically, shooters often use ball powders when reloading the 5.56 for their ARs because it meters more accurately from a powder throw than log powders.
Another factor that comes into play is that somewhere along the line, somebody decided to sell the new rifle as "self cleaning" and it was issued with no cleaning gear or instructions. While the gummy powder residue from the ball powders alone would not have been an issue, combined with the inability of the troops to perform the most routine of maintenance, deletion of the chrome lined bore and the harsh environment of the jungles of Vietnam, the M16 was doomed to fail from the start.
In reality, the reputation of the M16 for poor reliability stems from political finger pointing to avoid having to take responsibility for poor choices rather than any design flaw. I grew up being told that the original tolerances of the M16 were loosened up for better functioning. Yet, from what I understand, you can take a bolt and carrier made today and use it in an original M16 and vice-versa. (If this is wrong, please correct me). The basic action design remains intact
you are correct.
also you can use an original M16 BCG in a current day AR-15 and it fits perfectly. when the M16 was introduced it honestly was doomed from the start.
wild_wild_wes
02-15-12, 16:43
Cleaner? What exactly does that mean? Stoichiometrically, the ratio of powder to byproduct (carbon, gasses, etc) is a fixed number for a given load. I.E. one round of M855 produces the same mass of byproduct in a DI coaxial system as it does in a conventional piston system. The issue to be argued is where that byproduct goes. The belief that carbon fouling will have an adverse effect on the tolerances of a DI piston system but not a typical piston system is irrational as the two systems are functionally the same.
Fancy +3 syllable words like "stoichiometrically" will not win over the masses to your logic, but catchy non-sequiturs like "shits where it eats" will...
No rifle is godly.
The stoner system is also far more reliable than most give credit for, its far from fragile even in harsh environments. Like i said go look at the OEF, and OIF thread up top and youll have 6 pages of memebers who never had a single stoppage.
Its not a perfect system but none are, but the stoner design is a good combat rifle that has served out military well and will continue to do so until something revolutionary comes out.
I do agree with montrala that depending on one country for parts for uour armies rifles would be a hassle but the stoner system certainly isnt fragile like he mentions
I think if you haven't had a malfunction with any rifle, be it an AK or AR15, you haven't shot it enough, or shoot under perfect conditions, or haven't shot multiple examples. So I don't believe anybody that says they never had a malfunction with any rifle.
Thank you, mist. Much more eloquent than I, and maybe we can put some of this to bed.
Like that's gonna happen.
Well, at least you put it in black and white for us. Much appreciated.
sinlessorrow
02-15-12, 17:04
I think if you haven't had a malfunction with any rifle, be it an AK or AR15, you haven't shot it enough, or shoot under perfect conditions, or haven't shot multiple examples. So I don't believe anybody that says they never had a malfunction with any rifle.
so I guess every one in those 6 pages are a liar because their rifles never had a stoppage during engagements?
please be my guest and go tell the veterans on this website they are a liar
I never said that the posters never had any stoppages in their time shooting, all I said was they never had a stoppage during engagements(which is when it matters). according to surveys 81% of soldiers who enter combat never experience a stoppage during combat. the 19% that do experience a stoppage report that 50% of them were caused by magazines
Suwannee Tim
02-15-12, 17:17
.....You have essentially for an example argued that coal turbine.....
A coal turbine? What the heck is that?
so I guess every one in those 6 pages are a liar because their rifles never had a stoppage during engagements?
please be my guest and go tell the veterans on this website they are a liar
I never said that the posters never had any stoppages in their time shooting, all I said was they never had a stoppage during engagements(which is when it matters). according to surveys 81% of soldiers who enter combat never experience a stoppage during combat. the 19% that do experience a stoppage report that 50% of them were caused by magazines
You left that detail out. What survey? Magazine failures counts every bit as much as rifle failures seeing how the a rifle can't run with well with bad magazines.
sinlessorrow
02-15-12, 17:35
You left that detail out. What survey? Magazine failures counts every bit as much as rifle failures seeing how the a rifle can't run with well with bad magazines.
the CNA survey taken in 2006 that interviewed 2600 soldiers just coming from active duty. it included the M4, M16, M9, and M249
overall only 5% of the 2600(around 137) thought the M4 should be replaced due to its susceptible to the elements
I also agree magazine failures count but they can easily be remedied by using a quality polymer mag like a PMAG or a Lancer that are far stronger and far more reliable than USGI mags
Sinlessorrow:
A piece of friendly advice, seeing as you state many things as fact, would be to back what you say up with proper data. Maybe excerpts from documents.
That way readers will be able to differentiate what is merely your opinion, and what someone else has documented via quantifiable data.
Here is the CNA survey:
Soldier Perspectives on Small Arms in Combat
http://images.military.com/pix/defensetech/cna_m4_study_d0015259_a2.pdf
--------------------------------------------------
One of the more recent incidents leading to media critique of the DI system, was the Battle of Wanat in 2008, where 9 US servicemembers lost their lives.
@Eric D.:
You stated the following:
Furthermore, the temperatures reached as a result of the M4's sustained rate of fire are not enough to be a detriment to the bolt. The critical temperature, the temperature at which any heat treating effects are reversed, for an average steel is 1300 degrees F.
I know that you say "the bolt", and that might be true, but the fact is that heat WILL have an adverse effect on any weapon system. If you push the weapon beyond it's limits in so far as cyclic fire goes, without allowing for cooling, the weapon system will be more prone to failure.
First, here is an article outlining some of the critique after the battle:
http://www.usni.org/magazines/proceedings/2010-07/what-really-happened-wanat
An interesting paragraph:
Rounds per Minute
According to U.S. Special Operations Command's SOPMOD (special operations peculiar modification) program office, "The current sustained rate of fire for the M4A1 Carbine is 15 rounds per minute and a maximum rate of 90 [rounds] per minute for short periods in an emergency."18 Firing the M4 carbine at cyclic rates of fire of 90 to 150 rounds per minute, "which is the rate of suppressive fire associated with machine guns" for prolonged periods leads to rapid heating of the barrel and possible failure.19
Tests conducted by both the Army and by Colt indicate that "exceeding the sustained rate of fire of 15 rounds per minute will result in the weapon 'cooking off' rounds after approximately 170 rounds have been fired." If the maximum rate of fire of 90 rounds per minute "is maintained for about 540 rounds, the barrel softens and gas starts to blow by the bullet, changing the sound and size of the muzzle blast." If the operator continues to fire the weapon, the barrel will begin to droop, and finally, at about 596 rounds, the barrel will burst.
Here is a link to the official report:
http://usacac.army.mil/cac2/cgsc/carl/download/csipubs/Wanat.pdf
A paragraf regarding the weapons failures:
During the engagement, some of the platoon’s weapons failed. A superficial examination of these failures may lead to the conclusion that the root causes were either inherent to the weapons’ design or lay in poor maintenance by the operators. However, a more systematic analysis of weapons usage shows that almost all of the weapons that failed did so after firing a high volume of rounds in a short period. While about a fifth of the weapons failed sometime during the action, all but one of these cases occurred after the weapons were fired at a high rate for a number of minutes. The one exception was a SAW from the engineer squad that initially failed to fire but after a routine barrel change was back in action. Several other SAWs also jammed but their operators were able to put them back into working order. There is no conclusive evidence that the weapons’ failures led to any of the casualties at COP Kahler.
Now, would it have made a difference if they had used a piston system, in regards to it's supposedly cooler operation? I don't know. Our technical manual states that the weapon should be allowed to cool off after firing 180 rounds during sustained fire, to avoid cook-off's.
The barrel of our HK416's can get pretty hot.
--------------------------------
@Montrala:
I know what has been stated on HKPro, by G3Kurz. Although it could be true, we have to acknowledge that without any official documentation, it is purely anecdotal data.
My own observations indicate that the weapon is very robust, but I would be very interested in seeing a document similar to the MIL-DTL of the M4A1 Carbine, to see what the requirements actually are.
sinlessorrow
02-15-12, 21:16
You are correct Arctic, I should have spent more time linking facts and for that I am sorry.
The battle of Wanat is one of the reasons we went to a heavier barrel.
The other thing about Wanat was the area was not guarded enough, we had 40 people there knowing the amount of insurgents that could attack. Sadly they felt 40 men would be enough and sadly it was not. Wanat was a failure in leadership, i think one reason the M4 melted down there was because they were matching the fire rate of the enemy.
Only having 40 men there makes it difficult to match fire rates of 100 men. That said the M4 did hold its own in the battle and i think had they had M4A1's with their heavier barrel they would have held out longer. The m4 failures had nothing to do with the DI system but more about how they were used(on full auto constantly)
You are correct Arctic, I should have spent more time linking facts and for that I am sorry.
The battle of Wanat is one of the reasons we went to a heavier barrel.
The other thing about Wanat was the area was not guarded enough, we had 40 people there knowing the amount of insurgents that could attack. Sadly they felt 40 men would be enough and sadly it was not. Wanat was a failure in leadership, i think one reason the M4 melted down there was because they were matching the fire rate of the enemy.
Only having 40 men there makes it difficult to match fire rates of 100 men. That said the M4 did hold its own in the battle and i think had they had M4A1's with their heavier barrel they would have held out longer. The m4 failures had nothing to do with the DI system but more about how they were used(on full auto constantly)
Fully automatic? I always thought the M4's issued to regular army and Marines were strictly M4's with the lighter barrel profile, and that M4A1's were not standard and were issue to SF. Correct me if I'm wrong though.
sinlessorrow
02-15-12, 21:39
Fully automatic? I always thought the M4's issued to regular army and Marines were strictly M4's with the lighter barrel profile, and that M4A1's were not standard and were issue to SF. Correct me if I'm wrong though.
Pretty sure the guys at wanat had auto M4's even the links Arctic posted stated so. It said the troops were running the guns on auto to keep fire rates equal to the 200 assaulting insurgents
you should also check out Arctics post
here is one very good quote from here http://usacac.army.mil/cac2/cgsc/carl/download/csipubs/Wanat.pdf (page. 144)
Without any machine guns of their own, the mortarmen had to use M4 assault rifles firing at the maximum rate of fire simply to suppress the enemy in order to survive. In this way, Phillips burned out a series of three M4s.
page. 149
To achieve this effect with the available weapons, the 2d Platoon paratroopers were forced to fire their small arms at the maximum cyclic rate. The initial fight at the mortar pit, described earlier in this chapter, illustrated this. In other positions as well, the SAWs and, in particular, the M4s, experienced difficulty maintaining such a rate after the barrels got excessively hot.
this is one of the most important notes on pages 219-220
The concept of employment of weapons in an infantry platoon directed crew-served weapons to provide high rates of fire capable of suppressing enemy positions. These weapons, M240 machine guns and SAWs especially, were designed for such use and were equipped with belt-fed ammunition and extra barrels. No M240s failed in the action and the SAWs that jammed, did so after firing a great number of rounds. As noted above, these jams were fixed when the operators changed barrels. In fact, most of the weapons that jammed at Wanat were M4 carbines. The M4 was the basic individual weapon carried by US Soldiers in Afghanistan and was not designed to fire at the maximum or cyclic rate for extended periods. Enemy action and weapons dispositions forced the defenders of COP Kahler and OP Topside to use their M4s in uncharacteristic roles. This, not weapons maintenance deficiencies or inherent weaknesses in weapons design, was the reason a number of weapons jammed during the battle.
wild_wild_wes
02-16-12, 00:16
Well, there you have it. The M4 is an assault rifle, not an MG.
A coal turbine? What the heck is that?
It's something relevant to an M4. Duh.
My roommate, when he got back from Iraq, promptly built himself an AR-15. If he had had a bad experience with them (which I asked--he did not, except he did say Marines do DUMB! shit with their gear that compromises it sometimes...) I doubt he would have done this.
Why do so many people promptly come back from the sand-box and buy M4/AR's? If they are so bad, why spend your OWN money on one after that horrible experience with an unreliable rifle?
The evidence suggests that they work just fine.
Pretty sure the guys at wanat had auto M4's even the links Arctic posted stated so. It said the troops were running the guns on auto to keep fire rates equal to the 200 assaulting insurgents
you should also check out Arctics post
here is one very good quote from here http://usacac.army.mil/cac2/cgsc/carl/download/csipubs/Wanat.pdf (page. 144)
Without any machine guns of their own, the mortarmen had to use M4 assault rifles firing at the maximum rate of fire simply to suppress the enemy in order to survive. In this way, Phillips burned out a series of three M4s.
page. 149
To achieve this effect with the available weapons, the 2d Platoon paratroopers were forced to fire their small arms at the maximum cyclic rate. The initial fight at the mortar pit, described earlier in this chapter, illustrated this. In other positions as well, the SAWs and, in particular, the M4s, experienced difficulty maintaining such a rate after the barrels got excessively hot.
this is one of the most important notes on pages 219-220
The concept of employment of weapons in an infantry platoon directed crew-served weapons to provide high rates of fire capable of suppressing enemy positions. These weapons, M240 machine guns and SAWs especially, were designed for such use and were equipped with belt-fed ammunition and extra barrels. No M240s failed in the action and the SAWs that jammed, did so after firing a great number of rounds. As noted above, these jams were fixed when the operators changed barrels. In fact, most of the weapons that jammed at Wanat were M4 carbines. The M4 was the basic individual weapon carried by US Soldiers in Afghanistan and was not designed to fire at the maximum or cyclic rate for extended periods. Enemy action and weapons dispositions forced the defenders of COP Kahler and OP Topside to use their M4s in uncharacteristic roles. This, not weapons maintenance deficiencies or inherent weaknesses in weapons design, was the reason a number of weapons jammed during the battle.
So multiple M4's were "burned out"?
Barrels got too hot?
Sounds like if it's reliable enough to go "bang" so many times, so quickly, that it melts the barrel, it's G2G. I doubt they were stopping to lube every few magazines. Great endorsement of the system when a GI's individual weapon is reliable enough to melt the barrel before it is taken out of service by some malfunction.
sinlessorrow
02-16-12, 00:53
So multiple M4's were "burned out"?
Barrels got too hot?
Sounds like if it's reliable enough to go "bang" so many times, so quickly, that it melts the barrel, it's G2G. I doubt they were stopping to lube every few magazines. Great endorsement of the system when a GI's individual weapon is reliable enough to melt the barrel before it is taken out of service by some malfunction.
pretty much, the document does not go into great detail but from what I can gather they melted it down, one guy said his M4 was so hot he could not charge it anymore so he threw it down and grabbed a different rifle.
the combat in Wanat was non stop for 3.5 hours so there was no lubing their rifles in the middle of combat, so yes I agree, it is a very good endorsement for the M4, you should also note that not every M4 melted down, just the ones that were forced to be used like the M249.
wild_wild_wes
02-16-12, 00:57
Here is a silly video for you to watch:
http://video.nytimes.com/video/2010/01/12/world/asia/1247466496255/m-4-firing-test.html
Do any of you think you will ever run your AR that hard...
sinlessorrow
02-16-12, 00:59
Here is a silly video for you to watch:
http://video.nytimes.com/video/2010/01/12/world/asia/1247466496255/m-4-firing-test.html
Do any of you think you will ever run your AR that hard...
very good video, that was actually done by Colt after Wanat, there is a different video where they used a heavy barrel now in use on new M4's and it went 900 rounds
Here is a silly video for you to watch:
http://video.nytimes.com/video/2010/01/12/world/asia/1247466496255/m-4-firing-test.html
Do any of you think you will ever run your AR that hard...
Well, what I have tried to do is provide some hard data that will attest to the durability of the standard DI platform.
I guess some people are hard to please.
sinlessorrow
02-16-12, 10:10
Well, what I have tried to do is provide some hard data that will attest to the durability of the standard DI platform.
I guess some people are hard to please.
I do not think that was aimed at you Arctic, I actually enjoy your posts. Your one of those HK uses who also realizes other systems make great combat rifles as well
Failure2Stop
02-16-12, 10:20
Well, what I have tried to do is provide some hard data that will attest to the durability of the standard DI platform.
I assure you, it has not gone by unnoticed.
It is a testament to integrity and perspective that someone that is issued the "best" "piston" AR derivative understands the real issue and doesn't fixate on what method is used to push the BCG back and forth.
wild_wild_wes
02-16-12, 10:32
I do not think that was aimed at you Arctic. Your one of those HK uses who also realizes other systems make great combat rifles as well
It wasn't. I posted that vid to make the point that the weapons failed because they were misused and pushed past their design parameters.
sinlessorrow
02-16-12, 11:41
It wasn't. I posted that vid to make the point that the weapons failed because they were misused and pushed past their design parameters.
That is exactly why the M4's at Wanat failed. None of the rifles failed because of the operating system, it was how they were used.
One person who survived said his M4 got so hot he could no longer hold it and had to grab a different rifle
That is exactly why the M4's at Wanat failed. None of the rifles failed because of the operating system, it was how they were used.
One person who survived said his M4 got so hot he could no longer hold it and had to grab a different rifle
Even as far back as Vietnam, the M16 had reputation of overheating easily on fully automatic. So one could partly say the operating system is a culprit. The Marine Corps rejected a sustained fire version of the M16. Aluminum alloys are also not as good with heat resistance as steel is. Chamber pressures of the 5.56x45 are also higher then many rounds like the 7.62x39 and 7.62x51. Plus it doesn't fire from the open bolt. If piston or heavier barrel would have changed the outcome, I don't know.
@Failure2Stop:
Roger, and thanks.
@Wild_Wild_Wes:
Roger, no worries. Tone is sometimes hard to make out on the net.
wild_wild_wes
02-16-12, 13:58
Even as far back as Vietnam, the M16 had reputation of overheating easily on fully automatic. So one could partly say the operating system is a culprit. The Marine Corps rejected a sustained fire version of the M16. Aluminum alloys are also not as good with heat resistance as steel is. Chamber pressures of the 5.56x45 are also higher then many rounds like the 7.62x39 and 7.62x51. Plus it doesn't fire from the open bolt. If piston or heavier barrel would have changed the outcome, I don't know.
I don't think so. The problm was expecting a <6 lb. compact carbine to function as a sustained fire machine gun. If the M4 is correctly lubricated, as the video I posted shows you can fire mag after mag on full-auto...until the barrel melts.
sinlessorrow
02-16-12, 14:46
I don't think so. The problm was expecting a <6 lb. compact carbine to function as a sustained fire machine gun. If the M4 is correctly lubricated, as the video I posted shows you can fire mag after mag on full-auto...until the barrel melts.
Exactly, its not the operating system its the barrel that overheats.
Being DI doesnt change the amount of heat the barrel gets.
A heavier barrel like the one issues on M4A1's now can go much longer than the government barrels they had at wanat. The test Colt did shows the barrel easily outlasts the gas tube(which still took over 600 rounds to melt). I think the test ended at 900rounds
I don't think so. The problm was expecting a <6 lb. compact carbine to function as a sustained fire machine gun. If the M4 is correctly lubricated, as the video I posted shows you can fire mag after mag on full-auto...until the barrel melts.
If soldiers had their rifles in vices and didn't have to touch the handguards, then it would be a great test. And different operating conditions have to be taken into mind. I'd also think a barrel will heat up more in conditions like Afghanistan, rather then on a ventilated test range.
Thomas M-4
02-16-12, 16:15
If soldiers had their rifles in vices and didn't have to touch the handguards, then it would be a great test. And different operating conditions have to be taken into mind. I'd also think a barrel will heat up more in conditions like Afghanistan, rather then on a ventilated test range.
So what now the wide out doors are not ventelated enough how about a mountain top?? :sarcastic:
Yea it was in a vice because because 99.9% would not be able to hold the weapon if it got that hot the point is it ran until the barrel got so hot it drooped and a bullet went out the side of it the thats even whith the gas tube being pulled out of alginment when the barrel started to droop. The test only showed the weakest part which was the barrel the operating system still functioned even after being compromised.
sinlessorrow
02-16-12, 16:17
If soldiers had their rifles in vices and didn't have to touch the handguards, then it would be a great test. And different operating conditions have to be taken into mind. I'd also think a barrel will heat up more in conditions like Afghanistan, rather then on a ventilated test range.
Thats true, but again it has nothing to do with operating systems. There are tests listed that shows the barrel/gas block get the same temp be it piston or DI.
The M4's barrels failed that would have happened with a piston too.
@esh325:
Well, then it is air cooling that is a poor concept, not what cycles the action.
All weapons experience this issue, regardless of operating system used. Why do you think there is a set barrel swap interval for LMG's, MMG's and HMG's? Why do they operate from an open bolt design? To avoid cook off's due to barrel heating.
Failure2Stop
02-16-12, 16:27
If soldiers had their rifles in vices and didn't have to touch the handguards, then it would be a great test. And different operating conditions have to be taken into mind. I'd also think a barrel will heat up more in conditions like Afghanistan, rather then on a ventilated test range.
I fail to see your point.
@esh325:
Well, then it is air cooling that is a poor concept, not what cycles the action.
All weapons experience this issue, regardless of operating system used. Why do you think there is a set barrel swap interval for LMG's, MMG's and HMG's? Why do they operate from an open bolt design? To avoid cook off's due to barrel heating.
I never said they didn't experience this issue. They will all cook off and heat up. The question is when?
Thats true, but again it has nothing to do with operating systems. There are tests listed that shows the barrel/gas block get the same temp be it piston or DI.
The M4's barrels failed that would have happened with a piston too.
I never said it failed because it was a DI. It's the whole rifle itself.
sinlessorrow
02-16-12, 16:39
Esh its the barrel, one person in that document said he fired 12 magazines in under 20 minutes, at that point the handguards were to hot to hold so he had to grab a different rifle.
Thats almost double the standard combat load in 20 minutes, with a government profile barrel its going to get hot fast and fail fast when going full auto.
Thats one reason SOCOM wanted a heavy barrel(which all M4A1's now have)
They take longer to heat up and can withstand more heat
It has nothing to do with the operating system or the rifle, its the barrel. That is why LMG's and such have open bolt firing and swappable barrels. Open bolt helps cool down the barrel and when it gets too hot you swap it out.
During normal operations the M4A1 should not get to the point that it would need a barrel swap, sadly the circumstances in Wanat forced them to operate their rifles in ways they are trained not to
@Esh:
You say:
It's the whole rifle itself.
Based on that observation you are saying that all small arms designs that uses a barrel, a projectile and gunpowder as propellant, are flawed.
Like it has been stated, the difference is in the barrel. Here is a vid of the M4A1 being fired up to it's breaking point:
http://video.nytimes.com/video/2010/01/12/world/asia/1247466496261/m-4a1-firing-test.html
Data from the test:
Barrel Smolders and Glows: 1:48
Guard Assembly Catches Fire: 2:22
Fails to Fire Automatic: 4:47
Shots Fired: 911
The previous M4 video, and data:
http://video.nytimes.com/video/2010/01/12/world/asia/1247466496255/m-4-firing-test.html
Barrel Droops: 1:20
Barrel Ruptures: 1:51
Shots Fired: 535
As far as I know, the only differences between the M4 and the M4A1 is the FA capabilty, H2 buffer and heavier and different profiled barrel.
These two factory tests clearly show that the design is not the issue, barrel design is.
It should be said that the M4 used in the test was modified to be able to fire in fully automatic mode, and that the rate of fire shown in the video is unrealistic when compared to an in-service version only capable of 3rd bursts.
Still, the rate of fire maintained during the contact, 12 mags in under half an hour, was enough to effect the weapon negatively when combined with the local temperature.
It is not designed to be used in a sustained fire role.
I would like to end my post, with a paragraph from the paper written by Major Thomas Ehrhart:
Increasing Small Arms Lethality in Afghanistan:
Taking Back the Infantry Half-Kilometer
http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA512331&Location=U2&doc=GetTRDoc.pdf
There are four primary causes of malfunctions in the M4/M16. They are first, worn/unserviceable magazines, followed by a lack of proper lubrication, then worn parts, specifically the components of the bolt, and finally dirty ammunition.
That sums it up quite nicely, and does not touch on carbon fouling or operating system. He touches on these four causes in detail later in the paper.
...and dumping a 500 rounds in less than 2 minutes is relevant to what %'age of users?
It works just fine.
Esh its the barrel, one person in that document said he fired 12 magazines in under 20 minutes, at that point the handguards were to hot to hold so he had to grab a different rifle.
Thats almost double the standard combat load in 20 minutes, with a government profile barrel its going to get hot fast and fail fast when going full auto.
Thats one reason SOCOM wanted a heavy barrel(which all M4A1's now have)
They take longer to heat up and can withstand more heat
It has nothing to do with the operating system or the rifle, its the barrel. That is why LMG's and such have open bolt firing and swappable barrels. Open bolt helps cool down the barrel and when it gets too hot you swap it out.
During normal operations the M4A1 should not get to the point that it would need a barrel swap, sadly the circumstances in Wanat forced them to operate their rifles in ways they are trained not to
100% correct.
I never said it failed because it was a DI. It's the whole rifle itself.
Off the top of my head, ak handguards catch fire after about 3 or 400rds (edit round reference http://www.youtube.com/watch?v=eNAohtjG14c)
I donno how reliable that source is, but if true, it seems both guns get too hot to hold after similar round counts.
As stated, its inherent to firearms, unless you start insulating your HG with aerogel, its gonna get hot.
Esh its the barrel, one person in that document said he fired 12 magazines in under 20 minutes, at that point the handguards were to hot to hold so he had to grab a different rifle.
Thats almost double the standard combat load in 20 minutes, with a government profile barrel its going to get hot fast and fail fast when going full auto.
Thats one reason SOCOM wanted a heavy barrel(which all M4A1's now have)
They take longer to heat up and can withstand more heat
It has nothing to do with the operating system or the rifle, its the barrel. That is why LMG's and such have open bolt firing and swappable barrels. Open bolt helps cool down the barrel and when it gets too hot you swap it out.
During normal operations the M4A1 should not get to the point that it would need a barrel swap, sadly the circumstances in Wanat forced them to operate their rifles in ways they are trained not to
^Excellent
Good info in this thread, and thank you to those that posted the links to the videos and provided info!
Serious question:
In some battles, such as Ia Drang and Mogadishu, M16s were fired heavily over a long period of time. Yet reading the after-action report for Ia Drang, Col. Moore didn't mention any burned up rifles, cook offs, or similar problems. And this was with the original pencil barrel M16A1.
http://www.lzxray.com/documents/aar-xray.pdf
Soldiers: what gives?
sinlessorrow
02-17-12, 17:11
Serious question:
In some battles, such as Ia Drang and Mogadishu, M16s were fired heavily over a long period of time. Yet reading the after-action report for Ia Drang, Col. Moore didn't mention any burned up rifles, cook offs, or similar problems. And this was with the original pencil barrel M16A1.
http://www.lzxray.com/documents/aar-xray.pdf
Soldiers: what gives?
OK, I finally had time to read over that quickly. From what I read it mainly said heavy firefights, but it never once said the M16's had to be used in ways they were not made to.
at Wanat, they literally used their M4's like that of a M249. Magazine after Magazine firing as fast as possible.
One of the criticisms of the Stoner gas system is that it carries heat to the BCG, yet no one can answer how much heat is still in the gas when it reaches the BCG. Earlier in the thread, this was posted-
I would like to take a moment to debunk this "fact".
Empirical evidence? Here you go:
https://www.m4carbine.net/showthread.php?t=57400&highlight=sr556c
This link takes us to a test comparing the temperature differences between a Colt M4 and a Ruger SR556. At the BCG, it isn't much at all. After 5 magazines, the bolt of the M4 was 126 degrees and the Ruger was 87, a difference of about 40 degrees. While the M4 bolt was hotter, it's not as hot as some critics would lead us to believe.
The standard gas block has a small expansion chamber in it. When the gases pass from the gas port and enter this chamber, pressure drops. This causes the gas to dump some of the heat it's carrying. Considering it's such a small volume, it may not be very much. But look at the difference in temperatures between the BCG and the gas block. Gas blocks measured between 180 and 200 degrees. That's almost 100 degrees hotter than the bolt.
I recently took my carbine out and put 480 rounds through it in a day. First thing I did I fired a couple of thirty round magazines at a fairly brisk pace from a cold rifle, shooting fast, but taking time to keep my shots on target. Right after, I pulled the BCG out. It was slightly warm to the touch but only the gas key was uncomfortably so. The rifle was re-assembled and we started our shooting. This is my carbine.
http://i115.photobucket.com/albums/n289/SgtSongDog/AR%20Carbine/CarbineSurefire003.jpg
It's a PSA rifle kit assembled on a PSA lower. Barrel is a government profile stainless steel made by (I'm told) by Wilson.
At the end of the day, I let my rifle sit for a few moments to snap a few photos of the carbon residue left on the Surefire X300. I then opened the rifle and carefully removed the BCG, thinking it would be pretty warm, if not hot. It was warm, but not even enough to warm cold hands with. In fact, it was cooler than it was immediately after the first two mags and the gas key and bolt was no warmer than the carrier.
I checked the FSB by touch. I knew it was going to be hot from contact with a careless finger earlier. As I suspected, the FSB was painfully hot and possibly enough to cause burns. I splashed a bit of water on it and it skittered & steamed like on a hot griddle.
http://i115.photobucket.com/albums/n289/SgtSongDog/AR%20Carbine/DSC_0253.jpg
We didn't have a thermometer with us, but the FSB felt hotter than the barrel. However, since I didn't want to risk a burn, I didn't fondle either for very long!
My theory is that the gas block was designed as a heat sink to cool the gases before entering the gas tube. There is small expansion chamber which causes a drop in pressure and the gases throw off heat. This heat absorbed by the gas block and is radiated away. The gases are further cooled as they travel the gas tube. By the time they reach the action, there seems to be only enough heat left to warm the BCG. It seems the Stoner gas system deals with heat very well after all.
From all accounts, the biggest factor in dealing with heat generated from firing, is the barrel. While the barrel quickly gets too hot to touch from high volume fire, the rest of the rifle remains relatively cool. By the time the rifle gets too hot to hold, it has clearly been severely abused. Improving the heat sink capability of the barrel is more important to dealing with weapon heat than changing piston location
I did quite a bit of research a few years ago on a build. I was going to do a piston. the end result is you turn a AR into a AK. Both excellant platforms, But the Ar benefits from the gas operation. Less recoil more accuracy.
If you are running full auto or suppressed then the piston is a better mouse trap. Less dirt in action and crap coming back at you from running a can. Less heat in action from running full auto.
I don't run full auto or suppressed, so it's gas all the way for me.
I did quite a bit of research a few years ago on a build. I was going to do a piston. the end result is you turn a AR into a AK. Both excellant platforms, But the Ar benefits from the gas operation. Less recoil more accuracy.
If you are running full auto or suppressed then the piston is a better mouse trap. Less dirt in action and crap coming back at you from running a can. Less heat in action from running full auto.
I don't run full auto or suppressed, so it's gas all the way for me.
Can you cite a source? While I don't have a gas block piston upper to compare to my Stoner designed inline piston upper, my experience is that it's the gas block and barrel that gets hot, not the BCG. I didn't fire full auto or suppressed, mind you but if a gas block piston design is better for running either or both together, I'd like to see there is data showing it's because a gas block piston handles heat and residue better or if it's really for some other reason.
For example, how does a suppressor affect the gas system? By decreasing the velocity of the venting gases which increases the time needed to drop the system to atmospheric. It also increases the volume that is pressurized.
Another affect suppressors have on the gases is that it is an expansion chamber. High pressure high temperature gas enters through a small orifice into a larger volume which drops pressure and causes the gases to dump heat.
My question is, how much more residue is deposited in the action with an inline piston system compared to a gas block piston? The extra residue has to come from the gas tube as the residue from the bore is the same. Considering the difference in volume between gas tube and bore, how much greater is it's contribution?
How much greater could the deposits be inside the BCG from suppressor use? The pressure rise to move the carrier would remain the same. Any extra gas would be dumped into the receiver after the gas key separated from the gas tube.
It would be useful to know just how much of gas is carried back through the gas tube to the BCG. I don't have the math to figure it out
Failure2Stop
03-19-12, 10:57
I did quite a bit of research a few years ago on a build. I was going to do a piston. the end result is you turn a AR into a AK. Both excellant platforms, But the Ar benefits from the gas operation. Less recoil more accuracy.
If you are running full auto or suppressed then the piston is a better mouse trap. Less dirt in action and crap coming back at you from running a can. Less heat in action from running full auto.
I don't run full auto or suppressed, so it's gas all the way for me.
1- No, you most certainly do not "turn an AR into an AK", despite what the "Sons of Dumb" might say.
2- There are piston designs that are every bit as precise as a DI AR. Barrel quality trumps operating system where precision is concerned.
3- No matter what operating system you use, tons of crap gets blown into the lower and chamber when firing suppressed. You do get less gas in your eyes with a piston though.
4- Doesn't matter if you fire full auto or rapid semi auto when it comes to heat. Regardless, most of the heat issues occur when the round is in the chamber, as the barrel is what gets the hottest and retains the most heat, and is what leads to cook-offs.
5- The primary advantage of a piston is that it is far less finicky as far as changing ammo and variable gas pressure from running both suppressed and unsuppressed with short barrels.
Heavy Metal
03-19-12, 12:16
Aluminum alloys are also not as good with heat resistance as steel is.
AL is a far better heat sink. The choice of Aluminum for a upper reciever material is a far superior choice than steel. Aluminum can reject heat far more quickly and the AL upper helps remove excess heat from the chamber area.
Crow Hunter
03-19-12, 20:15
3- No matter what operating system you use, tons of crap gets blown into the lower and chamber when firing suppressed. You do get less gas in your eyes with a piston though.
Unless it is a M1A in an SAGE EBR chassis.:eek:
Then I got an eyeful, and a nose full, and I think some might have even gotten in my ear.:D
After being gassed my brother then mentions the Smith Enterprises gas block whatchamacallit than he "forgot" to turn to suppressed before he handed it to me. Yeah, right. :mad:
wild_wild_wes
03-19-12, 21:53
AL is a far better heat sink. The choice of Aluminum for a upper reciever material is a far superior choice than steel. Aluminum can reject heat far more quickly and the AL upper helps remove excess heat from the chamber area.
The last post on Page 4 states the importance of the gas block in syphoning heat out of the system. So, an aluminum gas block is better than a steel one?
Saleen4971
03-19-12, 22:08
AL is a far better heat sink. The choice of Aluminum for a upper reciever material is a far superior choice than steel. Aluminum can reject heat far more quickly and the AL upper helps remove excess heat from the chamber area.
Aluminum absorbs and dissipates heat faster. I think you two just aren't on the same terminology.
Sent from my MB860
Aluminum has the higher heat capacity which means higher heat transfer coeffictient. I would wager steel is used vs aluminum due to strength issues. Aluminum is softer than steel. The gas block has very hot gas flowing at a very high speed and pressure, with debris mixed in it.
I would bet the material was chosen for strength rather than heat sinking properties. The gap between the gas block and barrel may have been for heat though. This is just my reasoning. It would be interesting to know exactly why it was chosen, just for knowledge sake.
While aluminum is a better heat sink, steel is better at resisting gas cutting
On a suppressed AR there is enough gas coming back into the action that the shooter will get a puff in the face through the charging handle area. Piston doesn't have this as it's happening up front at the gas block.
Accuracy is a bit better with the gas system over the piston ( This is splitting hairs). Noveske purposly makes his barrel profiles thicker because he doesn't want a piston on his barrels.
On full auto guns the piston keeps the heat at the gas block and in the barrel. You can do a full auto dump, and open the gun and hold the BCG in your hand. It's cool.
The general word from most of the Military operators is the gas is a better system on the whole and the piston has it's place for suppressed and full auto
https://www.m4carbine.net/showthread.php?t=98475
Failure2Stop
03-20-12, 10:11
On a suppressed AR there is enough gas coming back into the action that the shooter will get a puff in the face through the charging handle area. Piston doesn't have this as it's happening up front at the gas block.
There is enough residual gas in the system after firing that you will get hit with a little gas after the shot, even with a 416. And, even with a piston upper, the lower gets filthy due to the retention and return of gasses. A little experience or research would reveal the truth in my statement.
Accuracy is a bit better with the gas system over the piston ( This is splitting hairs). Noveske purposly makes his barrel profiles thicker because he doesn't want a piston on his barrels.
Source regarding Noveske's reason for barrel profile?
I have seen no conclusive data that a decent piston appreciably decreases practical precision.
Here's an example:
https://www.m4carbine.net/showthread.php?t=32479
On full auto guns the piston keeps the heat at the gas block and in the barrel. You can do a full auto dump, and open the gun and hold the BCG in your hand. It's cool.
I've done the same with DI guns.
The gas key is hot, but the bolt face is relatively cool.
With either system, if you leave the bolt forward, the heat from the barrel will seep into the bolt/BCG and make them increasingly hotter. Moving the gas port forward does not change how hot the barrel gets, and barrel heat is the problem when it comes to heat-related issues with firearms.
The general word from most of the Military operators is the gas is a better system on the whole and the piston has it's place for suppressed and full auto
In an AR platform, I agree, in fact I think I said it as point #5 above.
I'm sorry if I am coming across as jumping on you, but it doesn't sound like you have much experience with suppressed piston ARs, and that you are just repeating words you have heard or read.
jonconsiglio
03-20-12, 10:23
I can't remember the last time I ran through a couple mags then thought that moment was the best time to take my bolt carrier group out of my rifle and play with it.
I run my rifles suppressed and occasionally full auto, including my SBR's. I still prefer DI. I own(ed) a couple piston ARs. I had a REPR and an MRP 12" that I sold. I still have an 8" PSD in 6.8. Not because I love the rifle, I rarely shoot it actually, but it fills a very specific role.
One of my primary rifles is a 10.5" LMT. It is extremely reliable regardless of how hard I push it. With a Vltor A5, it's even more consistent with different ammo, full auto and suppressed than it was with a carbine RE, though it always ran very well.
I have two SCARs as well. Since they are built from the ground up as piston rifles, I can't compare that part to a DI AR, though I can say that they are extremely reliable rifles. I would choose one of these long before I'd choose a piston AR. I'd still take a DI AR over either.
Failure2Stop
03-20-12, 10:34
I can't remember the last time I ran through a couple mags then thought that moment was the best time to take my bolt carrier group out of my rifle and play with it.
Lol, yeah, it was after a DI/Piston discussion when I had put forth the proposition that the lower operating temperature of the bolt in a 416 would increase longetivity that I was sent some data that showed that the operating temperature of bolts in both DI and piston guns were very close. So, I decided to verify with my highly scientific devices, the Mk2 Mod 0 fingertip.
jonconsiglio
03-20-12, 10:53
Lol, yeah, it was after a DI/Piston discussion when I had put forth the proposition that the lower operating temperature of the bolt in a 416 would increase longetivity that I was sent some data that showed that the operating temperature of bolts in both DI and piston guns were very close. So, I decided to verify with my highly scientific devices, the Mk2 Mod 0 fingertip.
That's awesome! How'd that work out for ya?
What gets me with these conversations is that it's inevitable that someone that has little to no experience with these rifles will pop in and state as a fact that you can immediately pull the BCG out of the rifle and play with it.
First off, who the hell does that? Well, besides our very own F2S…? :p
Second, What those very same people don't realize is what you (F2S) have already stated; whether it's piston or DI does not change how hot the barrel gets. With a bolt locked into the barrel extension of a hot barrel, it to will become hot.
Now, since we now have a rod working the BCG instead of hot gas, yes the gas key will get hot on a DI's bolt carrier. So what? What negatives are there to a hot gas key that a rod impacting it instead will fix?
I'm all for new and improved if it offers a serious benefit. Unfortunately, when these discussions come up, some of the most stupid points are used as the argument for one or the other.
"My BCG is cool to the touch" - This means little to me. If you told me my barrel stayed cool, then we'd be on to something.
"Piston rifles are less accurate" - Not in my experience. My REPR was very, very accurate. Both of my SCARs are crazy accurate. My 12" MRP was one of the most accurate CL AR's I've owned.
"Less gas in the face" - Again, I've run all of my rifles suppressed, and they all get dirty and blow back. Surprisingly though, my 14.5" BCM has absolutely no blowback, nor does my 10.5" LMT, and this is with 193, 855, 70gr TSX and 5.56 TAP 75gr, and I'm not even using a gasbuster or a modded CH.
If someone wants to buy a piston AR because it's easier to clean. . . Then my guess would be their priorities are a bit off. I'm all for people buying whatever rifle they want. BUT, don't get all emotional about it and go around spreading info that means very little. Speak about the facts. What it does or does not do that is truly better or worse than DI. Don't tell me it's easier to clean. That's just insanity.
Don't even bring up accuracy. I can't remember the last time I was shooting from anything but a bench or prone for groups to test accuracy that 1/2 MOA made any difference to me.
To me, and this is just for me, I only want to hear about durability, reliability, and how easy it is to obtain and replace broken parts. Don't get me wrong here guys, I'm all for an emotional-attachment-free discussion on the merits of both systems and when and where it applies. I just think way too many get excited about a cool bolt carrier (real or imagined), being easier to clean, and carrier tilt…which hasn't been a problem since what, 2001?
Just sayin'
Edit - In case I wasn't clear, I prefer a DI M4. I've tried piston versions and they're not for me, even when they're short barreled, full auto and suppressed. I don't hate them, I just prefer DI. I would not turn down an HK416, but that's not because I believe it's a better rifle, I'd just like to try one and find out for myself how it performs compared to my 10.5" LMT. At this point, I'd have no concerns taking a DI 10.5" to a fight.
Failure2Stop
03-20-12, 11:12
jon, agreed on all points.
sinlessorrow
03-20-12, 11:15
John I think you forget alot of people believe the TV.
I have had newbie gun owners praising pistons as a clean super cool(temp wise) system because of what they saw on future weapons
I dont know if you have seen that episode about the lwrci iar, but in it he dumps a mag in the lwrc and touches the BCG and says its still cold.
He then dumps a mag in a colt m4 and pours water on the barrel and talks about how much hotter the DI system runs.
Things like that are why people are ignorant about this stuff
jonconsiglio
03-20-12, 11:36
John I think you forget alot of people believe the TV.
I have had newbie gun owners praising pistons as a clean super cool(temp wise) system because of what they saw on future weapons
I dont know if you have seen that episode about the lwrci iar, but in it he dumps a mag in the lwrc and touches the BCG and says its still cold.
He then dumps a mag in a colt m4 and pours water on the barrel and talks about how much hotter the DI system runs.
Things like that are why people are ignorant about this stuff
Unfortunately, one 5 to 8 year old episode of Future Weapons is more than enough to convince many that the piston M4 is the superior rifle.
I hate to think this way, but I almost feel it should be strongly suggested people post where they get their info when they start praising, or condemning, one system or another. I'd be willing to bet that more than 50% are just repeating what they've heard. Sadly, it's probably a much higher number than that.
I've heard these arguments so many times before. I typically ask over what period of time with that particular rifle did it take for them to come to that conclusion. After about 5 seconds with that dear in headlights look, I'll get something to the effect of "Well, I don't own one, but I've heard…"
This goes for everything from piston vs DI, 9 vs 45, 50 vs 338, Surefire lights, Strider knives, etc.
Failure2Stop
03-20-12, 13:54
Unfortunately, one 5 to 8 year old episode of Future Weapons is more than enough to convince many that the piston M4 is the superior rifle.
I hate to think this way, but I almost feel it should be strongly suggested people post where they get their info when they start praising, or condemning, one system or another. I'd be willing to bet that more than 50% are just repeating what they've heard. Sadly, it's probably a much higher number than that.
I've heard these arguments so many times before. I typically ask over what period of time with that particular rifle did it take for them to come to that conclusion. After about 5 seconds with that dear in headlights look, I'll get something to the effect of "Well, I don't own one, but I've heard…"
This goes for everything from piston vs DI, 9 vs 45, 50 vs 338, Surefire lights, Strider knives, etc.
Good point, there should be some note on the forum about that.
Oh, wait, here we go:
Posting Suggestions
In order to maintain a site that is an effective database of good information, it is best to post information that you have first hand knowledge of. If you are repeating information that you have been told or have read from another poster, it is best to disclose that in the opening of the post.
Found in the "Rules", just beside the "Search" button, something else that few seem to find.
:laugh:
jonconsiglio
03-20-12, 14:24
Found in the "Rules", just beside the "Search" button, something else that few seem to find.
:laugh:
Awesome. I've had people get all bent out of shape when I've said that before.
militarymoron
03-20-12, 15:03
If someone wants to buy a piston AR because it's easier to clean. . . Then my guess would be their priorities are a bit off. I'm all for people buying whatever rifle they want. BUT, don't get all emotional about it and go around spreading info that means very little. Speak about the facts. What it does or does not do that is truly better or worse than DI. Don't tell me it's easier to clean. That's just insanity.
To me, and this is just for me, I only want to hear about durability, reliability, and how easy it is to obtain and replace broken parts.
i'm insane - just kidding. actually, that's one of the things that did attract me to piston guns when they first came out (easier cleaning). i'm an engineer, and have a natural curiosity about mechanical things, so i'm willing to try something different out, to see if it's better than the status quo.
i've limited experience shooting the HK416, LMT piston upper, various LWRCi uppers, and own the gen I and II PWS short stroke, and one ATAC GPU (PWS long-stroke piston) upper built by Addax. the ATAC long stroke has been one of my favourite uppers to shoot because it's been very reliable over a wide range of ammunition, and yes, easier to clean (more of a trivial reason).
here's what i've found after a few years of shooting it, as well as my DI uppers (note that i do not shoot suppressed or SBRs):
1. in general, the recoil impulse of piston guns i've shot is sharper than DI guns. it's noticeably sharper with the LWRCi and 416 (to me), while the ATAC long stroke feels like a DI gun.
2. i don't care about bolt or carrier temp. some might care about gas tubes melting/deforming, which might be a possible point of DI failure vs. a piston, but i'll never encounter that concern with the shooting i do.
3. all barrels and gas blocks get hot enough to burn me. i don't care which one gets hotter past that point.
4. the ATAC upper stays cleaner than a DI gun. once i've lubed it, the lube stays, and doesn't gum up. to me, this is more important than it being easier to clean - retaining lubrication in the operating parts, and not having to wipe down and relube after 500-750 rounds. i run the piston gun wet just like a DI gun.
5. 'easier to clean' doesn't mean it doesn't get dirty. it just gets dirty in a different location. the piston and piston tube get very dirty, but not the carrier/bolt/inside of the receiver. it just takes less time to get the ATAC to the same 'clean' condition than a DI gun after the same number of rounds. might be inconsequential to some, of course. it really is pretty trivial.
6. all piston AR uppers have carrier tilt. some manage it better than others, but it's always there. addressing carrier tilt and managing the wear associated with it, is NOT the same as claiming there's 'no carrier tilt'. i have a seth harness anti-tilt buffer that i use with the ATAC upper to manage it.
7. the long stroke ATAC cannot get a charging handle impingement malfunction because of the piston rod attached to the carrier in that space.
8. nothing has broken on it after about an estimated 5000 rounds through it, but if anything did break, parts replacement would be more of an issue than on a DI gun.
9. i do see more initial cam pin wear on the inside of the upper receiver with my piston guns than DI guns. hence that whole question about piston gun unlocking/extraction etc.
so, what have i learned, speaking solely with my experience with the ATAC upper and the other DI uppers i have? there's really not much difference between them in performance (assuming a good quality piston and DI upper). i've had some finicky DI uppers and others that gobble up anything (ever since i switched to the A5 buffer system). DI guns take a bit more lube on the bolt and carrier to keep running to the same round counts (on mine, anyways), and get messier. piston guns get dirty, but more of a dry dirty than gummy dirty.
given that i haven't found much practical difference between them in performance, i think the DI is a better logistical choice because the piston guns require non-standard parts. i have a lot of DI spare parts - no spare piston parts.
i'm not piston hater (because i'm happy with the piston upper i have), nor am i a 'piston is best' person either, since i have many more DI uppers than piston uppers, and shoot them just as frequently. to me, they're just different mechanical approaches to a particular issue, both with their pros and cons, which folks have to weigh for themselves. but i think that piston uppers start out with more mechanical challenges to overcome, from an engineering standpoint.
if someone already owned DI uppers and wanted to own a piston just because it's 'different', then i wouldn't stop them, but i'd try to make them aware of what they're getting into. if someone just getting into ARs wanted to know what rifle i'd start with, i'd recommend DI. note that i'm only speaking from my hobbyist/enthusiast point of view.
That's awesome! How'd that work out for ya?
What gets me with these conversations is that it's inevitable that someone that has little to no experience with these rifles will pop in and state as a fact that you can immediately pull the BCG out of the rifle and play with it.
First off, who the hell does that? Well, besides our very own F2S…? :p
I did. I've heard so many times that with the Stoner system routing the gas to the carrier, it heats up the BCG, I decided to test it for myself. It was lukewarm. Most, who talked about pulling the BCG of their gas block piston uppers to verify how cool it was after shooting always say "Try that with your DI!" and had never done it themselves. So I did. How'd it work out for me? BCG was barely warm to my Mk 2 Mod 0 fingertip :)
"My BCG is cool to the touch" - This means little to me. If you told me my barrel stayed cool, then we'd be on to something.
Ya know, I got so focused on whether or not the BCG got hot, I didn't stop to ask myself if it was even important.
Second, What those very same people don't realize is what you (F2S) have already stated; whether it's piston or DI does not change how hot the barrel gets. With a bolt locked into the barrel extension of a hot barrel, it to will become hot.
I was going to add that even after soaking, the BCG didn't get very warm, but then I realized that when I set the rifle down to shoot something else, I'd leave the bolt locked back.
My whole point in starting this thread was to explore what the Stoner system is and is not. So far, I've discovered it is a gas piston system. The piston is part of and inline with the bolt. It is not a conventional direct impingement system. Gases do act on the carrier but not in the same manner as a conventional DI system. Some of what I've discovered about the AR has busted many myths I was taught while growing up. A gunsmith friend of my father always claimed the AR was problematic and you had to keep it clean and only lightly lubed or residue would gum up it's tight tolerances. I've since learned, through personal experience, this is quite false. The AR will run dirty, runs better with lube and the fit of the carrier inside the upper isn't very tight.
I agree that the importance of the barrel in controlling weapon heat is largely overlooked by the average shooter
Heavy Metal
03-20-12, 16:06
The last post on Page 4 states the importance of the gas block in syphoning heat out of the system. So, an aluminum gas block is better than a steel one?
No, because the gas block is subject to pressures and temps beyond the ability of the material to handle. The reciever doesn't come close and the advantages outweigh the disadvantages for that application.
Notice the SCAR and the ACR both have AL recievers.
jonconsiglio
03-20-12, 16:33
I did. I've heard so many times that with the Stoner system routing the gas to the carrier, it heats up the BCG, I decided to test it for myself. It was lukewarm. Most, who talked about pulling the BCG of their gas block piston uppers to verify how cool it was after shooting always say "Try that with your DI!" and had never done it themselves. So I did. How'd it work out for me? BCG was barely warm to my Mk 2 Mod 0 fingertip :)
Good point. People just assume the piston carrier is nice and cold while the DI carrier is sizzling hot.
Ya know, I got so focused on whether or not the BCG got hot, I didn't stop to ask myself if it was even important.
Exactly. This is what I was saying earlier. Who cares if the carrier gets a little warm or not. What failure has ever been linked to a carrier that got a little hot?
I was going to add that even after soaking, the BCG didn't get very warm, but then I realized that when I set the rifle down to shoot something else, I'd leave the bolt locked back.
When I'm shooting, I usually just sling my rifle with the bolt forward. The only time I lock it back is after a heavier firing schedule… Or at the very least, clear the chamber and leave it closed. It is possible to have a cook off with both piston and DI rifles.
My whole point in starting this thread was to explore what the Stoner system is and is not. So far, I've discovered it is a gas piston system. The piston is part of and inline with the bolt. It is not a conventional direct impingement system. Gases do act on the carrier but not in the same manner as a conventional DI system. Some of what I've discovered about the AR has busted many myths I was taught while growing up. A gunsmith friend of my father always claimed the AR was problematic and you had to keep it clean and only lightly lubed or residue would gum up it's tight tolerances. I've since learned, through personal experience, this is quite false. The AR will run dirty, runs better with lube and the fit of the carrier inside the upper isn't very tight.
I've read your other threads about this and thought it was a very good observation. It's amazing the amount of bad info floating around with these rifles (all firearms in general). Must be extremely clean and lightly lubed to function… I've shot my guns very dirty and wet, and they ran just fine. I didn't do it because I'm neglecting my weapons on a regular basis, but more because I was at a class, or doing something similar, and I was just too tired to worry about it.
I do clean my primary rifles. Even though they've always functioned fine dirty, I'd still rather not take the chance. I don't do a thorough cleaning, just wipe the bolt carrier down and re-lube.
It amazing the things will tell others like it's fact, even though they've never experienced it and just heard it somewhere along the way. Don't even get me started about all the 1911 nonsense floating around!
I agree that the importance of the barrel in controlling weapon heat is largely overlooked by the average shooter
At least in my opinion, this is really the only part of the rifle that dealing with heat would be beneficial (including the bolt and barrel extension). Unfortunately for piston AR shooters, there's pretty much no difference in how the barrels handle heat from piston to DI. My SCARs get just as hot as my DI ARs.
Has the op satisfied his need for reassurance that the DI AR is "far" superior to any piston AR yet? This might not factor in for most shooters but how's the "DI inline piston" function with water in the gas tube? this subject doesn't seem to come up much when comparing DI to piston.
If you have something to add to the discussion, you're welcome to do so. If you see an error that needs correcting please point it out. If you're here to troll, make snide remarks or create a scene, please take it else where.
Thank you
This might not factor in for most shooters but how's the "DI inline piston" function with water in the gas tube?
After 53 years of service, this is all of a sudden a major problem in the Stoner design?
Water in the gas tube probably doesn't come up much because its really a non issue since 99% of folks don't spend any time in the water with their rifles. And those that do know that a simple tilt and shake should limit any issues related to water in their gas tubes.
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sinlessorrow
03-21-12, 10:55
Water in the gas tube probably doesn't come up much because its really a non issue since 99% of folks don't spend any time in the water with their rifles. And those that do know that a simple tilt and shake should limit any issues related to water in their gas tubes.
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All you have to do is charge the rifle or give gravity about 5 seconds to do its job.
jonconsiglio
03-21-12, 11:28
Back to my point in a previous post about how people will use the stupidest points (cold BCG, easier to clean and now water in the gas tube) when arguing piston vs DI.
Also… anyone that will be using a rifle professionally in a maritime environment will also have the training and knowledge needed to use their weapon in a maritime environment. Insane, I know.
If you have something to add to the discussion, you're welcome to do so. If you see an error that needs correcting please point it out. If you're here to troll, make snide remarks or create a scene, please take it else where.
Thank you
No offense. I'm can't knock the DI but I refuse to knock the piston as I have both and they hve both run equally well. I haven't had the piston setup long bu it seems to be running fine and to this point without any of the inherent problems of the piston AR. I just can't see how anyone that has utilized both could unequivocally say that one is "better" than the other. Maybe in time I'll find out.
I believe the issue is more of the of the piston system not offering any real advantages over DI rather than one being better than the other like the Piston is marketed.
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Failure2Stop
03-21-12, 13:07
I believe the issue is more of the of the piston system not offering any real advantages over DI rather than one being better than the other like the Piston is marketed.
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At a higher price point.
jonconsiglio
03-21-12, 13:11
I'm not sure why this always happens, but every time these debates come up, someone reads a little more into it and assume that by many of us choosing DI means we hate and speak badly of piston ARs.
I've owned both and put a high number of rounds through both. The piston AR offered no advantage for my needs, even though I often shoot suppressed and have short barrels.
So, even if they both performed equally, I'd choose the DI due to less moving parts, easier to obtain parts and the fact that I can use any hand guard I'd like and am not limited to just a few.
A piston vs DI fight? I've never seen one of those before. A mod should just make a piston vs DI sticky so everybody here can get out those piston vs DI urges.
sinlessorrow
03-21-12, 13:46
A piston vs DI fight? I've never seen one of those before. A mod should just make a piston vs DI sticky so everybody can tear so everybody here can get out those piston vs DI urges.
Sadly it didnt start this way.
Some people just believe choosing DI over a piston means we hate pistons, they then feel the need to defend their choice by using examples like water in the gas tube.
Sadly it didnt start this way.
Some people just believe choosing DI over a piston means we hate pistons, they then feel the need to defend their choice by using examples like water in the gas tube.
I'm guessing the result of water in the gas tube wouldn't be pretty. Seeing how we are fighting in the desert and that most people never be in a situation where water gets in the gas tube, it's a null argument.
It takes water in the barrel to make water in the gas tube.
Piston or DI water in the barrel is dangerous, its even dangerous in bolt and every other type of firearm, so realistically speaking, if someone is too stupid to know to crack the bolt and drain the barrel after immersion or even suspected immersion they kinda deserve everything that comes after.
Water in the gas tube isn't a DI issue, its a Darwin issue.
machinegunbob
03-21-12, 14:33
Go with a piston on a 10"gun,DI on anything above 11.5" and you will be find.
sinlessorrow
03-21-12, 15:38
Go with a piston on a 10"gun,DI on anything above 11.5" and you will be find.
I can honestly say I have never had issues with a 10.3" DI suppressed or not.
Piston or DI both get very dirty suppressed.
It takes water in the barrel to make water in the gas tube.
Piston or DI water in the barrel is dangerous, its even dangerous in bolt and every other type of firearm, so realistically speaking, if someone is too stupid to know to crack the bolt and drain the barrel after immersion or even suspected immersion they kinda deserve everything that comes after.
Water in the gas tube isn't a DI issue, its a Darwin issue.
Not my intention to add fuel to the fire, just posting the video to show that the OTB features of the HK416 works submerged, and that the premise of the above post is in error:
http://www.youtube.com/watch?v=AGwkHktkTxU
Not that the feature is a neccessity. I have never used it.
As far as the whole piston vs DI argument, I have no issues with either system, and I do not reside in either "camp". I'm pretty sure that there are bad eggs from both systems.
The only comment MistWolf has made that on the matter that I would disagree with, is the increased or higher recoil impulse of a piston system, caused by the offset piston.
If a DI (M4A1) and a piston rifle (HK416) fire the same round at the same velocity, the actual recoil impulse is the same. And the weapon velocity and free recoil energy is actually lower on the HK416. I can see that felt recoil however, as it is subjective in nature, can be different. If it is a piston system that is lighter than the 416, the velocity and free recoil energy would increase.
If this difference is attributable to the offset of the piston, I'm not so sure. There is not a lot of weight moving, and it does not move very far.
sinlessorrow
03-21-12, 17:33
I love when people post that video to justify a piston.
Please, the DI has been over the beach and back last time I checked. I'm also inclined to believe that video was setup.
If you watch it when he pulls the Hk416 out of the water you see water draining from the barrel. When the M4 comes out nothing drains.
Now even an M4 submerged will drain water from the barrel almost instantly, it then takes a few weconds for the gas tube to drain.
The fact that the barrel did not drain leads me to believe the bore was obstructed slightly.
Spikes tactical did a video on this. The guy pulled it out charged it and fired in 3 seconds. It took him 1-2 seconds toget the rifle shouldered and on target to engage.
So in a water test you are saving yourself 1 second by going piston.
@sinlessorrow:
You need to pump the breaks dude.
If you managed to read my post, I did not post the video to justify a piston system, I did it specifically to point out some errors in one post in regards to the OTB features of the HK416. Also, I was referring to the segment where it fires submerged, not when the weapons are pulled from the water. I didn't even say that the DI system will not work in this environment.
Nothing else. Find one post by me on this board where I unequivocally state the superiority of a piston system over the DI system, or bash the DI system, before you state that I am using a video in order to make cheap arguments in a fight I admittedly have no dog in.
Also, with this post and statements like "the test was a set-up", you are looking like the kind of people you insist you are not; DI users who hate pistons. I tried timing it, and he lets the HK416 drain for about 6 tenths of a second longer than the M4. That is well within the test parameters of max drain time <2 seconds. I am sure that the test parameters were supplied by the people who wanted the OTB feature.
sinlessorrow
03-21-12, 18:29
@sinlessorrow:
You need to pump the breaks dude.
If you managed to read my post, I did not post the video to justify a piston system, I did it specifically to point out some errors in one post in regards to the OTB features of the HK416. Also, I was referring to the segment where it fires submerged, not when the weapons are pulled from the water. I didn't even say that the DI system will not work in this environment.
Nothing else. Find one post by me on this board where I unequivocally state the superiority of a piston system over the DI system, or bash the DI system, before you state that I am using a video in order to make cheap arguments in a fight I admittedly have no dog in.
Also, with this post and statements like "the test was a set-up", you are looking like the kind of people you insist you are not; DI users who hate pistons. I tried timing it, and he lets the HK416 drain for about 6 tenths of a second longer than the M4. That is well within the test parameters of max drain time <2 seconds. I am sure that the test parameters were supplied by the people who wanted the OTB feature.
I did not realize it was you.
Honestly I think most tests are set up unless done by an outside company with no ties to the items being tested.
If Colt made a test like that I would say it was setup as well. Maybe that is ignorany of me, but one thing I have learned is every company has an agenda and what better way to fullfill it than by making a video.
My main point was the M4 has been over the beach and back, as has the HK416.
I despise that video and generally discredit the ones who post it. Had I looked at the poster(you) I would not have responded like I did.
I still think that video is rigged, just like ever infomercial we have in America are rigged.
machinegunbob
03-21-12, 19:25
I have had the 10.4"hk 416 upper on a full auto lower and ended up selling the upper and going back to a DI upper.I really did not see a real improvement in the piston upper.
Heavy Metal
03-21-12, 19:50
@sinlessorrow:
You need to pump the breaks dude.
If you managed to read my post, I did not post the video to justify a piston system, I did it specifically to point out some errors in one post in regards to the OTB features of the HK416. Also, I was referring to the segment where it fires submerged, not when the weapons are pulled from the water. I didn't even say that the DI system will not work in this environment.
Nothing else. Find one post by me on this board where I unequivocally state the superiority of a piston system over the DI system, or bash the DI system, before you state that I am using a video in order to make cheap arguments in a fight I admittedly have no dog in.
Also, with this post and statements like "the test was a set-up", you are looking like the kind of people you insist you are not; DI users who hate pistons. I tried timing it, and he lets the HK416 drain for about 6 tenths of a second longer than the M4. That is well within the test parameters of max drain time <2 seconds. I am sure that the test parameters were supplied by the people who wanted the OTB feature.
That 6/10ths of a second may have made all the diference. Plus, he tipped the muzzle of the 416 down a bit and lef the muzzle of the M-4 up a bit. The 416 is a fine rifle but that video stinks a bit.
Arctic1, you are correct that the recoil energy is the same regardless of the action type used.
What I said was that the inline piston system is used to reduce muzzle climb by keeping the recoil forces inline with the bore, bolt and shooters shoulder
An M16 can fire underwater too.
Provided the standard issue plastic muzzle cap is installed and it hasn't sat long enough for the receiver extension to fill.
Once it starts cycling general pressures involved will keep the barrel and gas tube empty of water while the RE will cyclically sump and discharge small amounts through the port in the buttstock mount screw.
'Course when you stop shooting and let it sit a while longer there can be problems unless deliberately drained with cracking the bolt back to break the bullet to chamber seal (think finger over end of drinking straw) a bit being a paramount step in the process.
Don't readily have video but know for sure it can be accomplished under those circumstances. (Engineer Lake, Ft. Polk, La. Don't ask)
Though the physics of a bullet in water puts a pretty big 'why?' on the actual value of firing that way regardless of means used to cycle the action. Popping up out of water to bust a few, sure, but to actually fire under water and expecting hits, let alone kills, is a bit of a reach as I imagine max range would be in the area of around 4 to 8 feet. Less in salt water. But if you got your muzzle right tight to the back of a divers head it could likely give a pink cloud of shark attractant.
Failure2Stop
03-21-12, 23:19
When it comes to submersion, there are a few different issues at play, and the DI 5.56 AR is behind the curve.
A bullet that hits water inside a barrel at high velocity is going to do wonky shit.
The small diameter bore of a 5.56 gun retains more water than a larger bore, and the percentage of water compared to bore volume will be higher with a smaller bore. A 7.62 bore is notably better in this regard than a 5.56 bore, even when the seal is broken by partially extracting the chambered round.
Ever notice that the submersion tests don't immediately preceed a precision test? Most barrels are going to be deformed in some way from the passage of the bullet with a water obstruction.
The gas tube is a vulnerability, though standard bore draining will take care of the tube well enough to work.
(Same thing with suppressors. While shooting them "wet" can work very well, that's not the same thing as "half full of water", which can be very exciting)
Water in the receiver extension can affect cycling, though it drains pretty well during bore draining.
If I had a job that required me to spend a lot of time with the gun under water and have to immediately employ the weapon from the water I would prefer a ground-up piston system with a large bore.
Interesting little post by Sinister a while ago:
A while ago... NSW winter warfare teams used 18" m14's w/ choate folding stocks. As compared to the m4, the more violent action enabled use in over the beach operations in freezing wx. Larger bore wouldn't retain water. Ballistic advantage of larger caliber.
(snip)
Recoil:
Felt recoil with a self-cycling firearm comes in 3 parts:
Initial recoil, caused by the equal/opposite action of accelerating a tiny bit of metal to supersonic speed from a resting state while encountering resistance. This can be reduced and extended by making the platform heavier, making the bullet lighter, reducing friction in the leade and rifling, and reducing acceleration (velocity, sorta).
Muzzle blast, caused by the jet action of the gasses exiting the bore. This can be reduced/extended/altered by slowing the exiting gasses, redirecting the gasses, reducing the volume of the exiting gasses.
Cycling the action, which causes the operating parts to be stopped by a part of the firearm to be returned to battery. This can be reduced/extended by altering the mass of the operating parts, altering spring resistance, softening the impact of the cycling action, and altering the velocity of the operating parts.
Arctic1, you are correct that the recoil energy is the same regardless of the action type used.
What I said was that the inline piston system is used to reduce muzzle climb by keeping the recoil forces inline with the bore, bolt and shooters shoulder
Muzzle rise, as I understand it is primarily a result of secondary recoil, ie the exiting of gases from the muzzle behind the projectile. These forces act down the centerline of the barrel, and on most rifles these forces are above the contact points a shooter has on the gun. That is why grip is important.
I cannot see the logic behind why the offset of the piston and oprod would cause increased muzzle rise, as the recoil forces produced (however minor) are in the same direction as the BCG, buffer and action spring when cycling.
I might not fully grasp the physics, but I am having a hard time wrapping my head around how an offset piston and oprod can cause an increase in muzzle rise.
Muzzle rise, as I understand it is primarily a result of secondary recoil, ie the exiting of gases from the muzzle behind the projectile. These forces act down the centerline of the barrel, and on most rifles these forces are above the contact points a shooter has on the gun. That is why grip is important.
I cannot see the logic behind why the offset of the piston and oprod would cause increased muzzle rise, as the recoil forces produced (however minor) are in the same direction as the BCG, buffer and action spring when cycling.
I might not fully grasp the physics, but I am having a hard time wrapping my head around how an offset piston and oprod can cause an increase in muzzle rise.
Because, on an ak for instance, the mass is higher than the contact point (fulcrum) of the stock. Think of holding a pistol at the bottom of the grip vs getting a high grip, which has more muzzle rise?
That said, I dont know if in a piston ar that would result in much more felt recoil/muzzle rise. It would depend on the mass of the piston also, and they are still pretty low and light compared to an ak.
The amount of kinetic energy of the gases and the bullet are identical(enought not to make a noticeable difference) regardless of the operating system. Both systems also get all the energy to operate during very short time period of few milliseconds it takes for the bullet to travel from the gas port to the muzzle.
Real differences in recoil come from the weight and speed of the BCG. Larger mass will cause more percieved recoil as well as faster moving BCG. Especially so if the BCG "collides" heavily in it's rear most position.
These are universal things, not AR specific.
In AR it is possible to change the percieved recoil by adjusting the gas port and by changing the weight of the buffer and the BCG and the action spring.
Ps. this video shows nicely three different guns right next to each other. It shows different recoil characteristics nicely. Notice how one of the guns gives very sharp violent vibrations that are pretty hard to control for the shooter:
http://www.youtube.com/watch?feature=player_embedded&v=bt41wNmau_8
Think of holding a pistol at the bottom of the grip vs getting a high grip, which has more muzzle rise?
Well, like I said:
These forces act down the centerline of the barrel, and on most rifles these forces are above the contact points a shooter has on the gun. That is why grip is important.
Meaning that the closer to the bore you grip the gun, the more you limit muzzle climb. This applies to both pistols and rifles.
And with the AK example, I do not think it is a matter of where the mass is located, as much as it is due to the fact that the stock, pistol grip and forearm are all located lower than the bore, where the recoil forces are generated. That is what causes the increased muzzle climb, not the offset piston.
AK's with inline stock are much easier to shoot fast than the ones with the traditional stock configuration.
Both systems also get all the energy to operate during very short time period of few milliseconds it takes for the bullet to travel from the gas port to the muzzle...
It takes longer than that. Carrier doesn't pressurize enough to start moving until after the bullet has cleared the muzzle and traveled several feet beyond. The gas pressure in the system doesn't drop to zero right away. It takes awhile for it to vent. While it's venting, at the beginning, there is still enough pressure to operate the rifle. I guess it's what is called an open system. Still, it's a short time
...with the AK example, I do not think it is a matter of where the mass is located, as much as it is due to the fact that the stock, pistol grip and forearm are all located lower than the bore, where the recoil forces are generated. That is what causes the increased muzzle climb, not the offset piston.
The offset piston does introduce offset forces during the firing sequence which act to pull the muzzle off target. The further away from the centerline, the greater the leverage the forces have. Increased mass and increased velocity of the offset reciprocating mass also increases the effect.
The inline piston eliminates the offset forces. This does not eliminate all muzzle rise as other factors come into play as well such as the stance of the shooter
AK's with inline stock are much easier to shoot fast than the ones with the traditional stock configuration.
I'm not really sure why the AK was never made with an in line stock in the first place. I've heard the argument that an in line raises your head higher off ground making you more of a target compared to a conventional drooped stock.
With an AK-74, none of that really matters anymore. The smaller round and muzzle brake negate that. They are said to have less recoil then most AR15's. Rifles with conventional operating rods having more recoil when compared to AR15's is mostly subjective
sinlessorrow
03-25-12, 15:18
I'm not really sure why the AK was never made with an in line stock in the first place. I've heard the argument that an in line raises your head higher off ground making you more of a target compared to a conventional drooped stock.
With an AK-74, none of that really matters anymore. The smaller round and muzzle brake negate that. They are said to have less recoil then most AR15's. Rifles with conventional operating rods having more recoil when compared to AR15's is mostly subjective
The muzzle brake has a lot to do with that.
If you take off the brake it has more muzzle rize, just like if you add a brake to an AR-15 you will have absolutely no muzzle rise, the diff is one has a ton of flash the other doesnt
...Rifles with conventional operating rods having more recoil when compared to AR15's is mostly subjective
This is frustrating. This has been explained over and over again.
The amount of recoil energy a cartridge generates remains the same regardless of action type it's fired in, whether it's semi-auto, full-auto, bolt action, pump action, revolver- what have you. It's not subjective, opinion, dependent on the phase of the moon or how you scatter chicken blood. It's physics, nothing more
The only changes to recoil energy the design of the action and ergonomics can make is how it affects the weapon and the shooter by changing the time and vector of the recoil energy distribution
I'm not really sure why the AK was never made with an in line stock in the first place. I've heard the argument that an in line raises your head higher off ground making you more of a target compared to a conventional drooped stock.
Yes they have been made with inline stocks. Examples of such design: Galil and RK95.
GunTotinRedneck
03-25-12, 16:53
DI guns are just fine. As the saying goes, "if it ain't broke, don't fix it!".
This is frustrating. This has been explained over and over again.
The amount of recoil energy a cartridge generates remains the same regardless of action type it's fired in, whether it's semi-auto, full-auto, bolt action, pump action, revolver- what have you. It's not subjective, opinion, dependent on the phase of the moon or how you scatter chicken blood. It's physics, nothing more
The only changes to recoil energy the design of the action ergonomics can make is how it affects the weapon and the shooter by changing the time and vector of the recoil energy distribution
That is the best I've heard it put forward. Thank you. Now can we put this to its much deserved rest?
I doubt it.
The offset piston does introduce offset forces during the firing sequence which act to pull the muzzle off target. The further away from the centerline, the greater the leverage the forces have. Increased mass and increased velocity of the offset reciprocating mass also increases the effect.
1. I cannot see why the recoiling of the piston and oprod would cause muzzle rise, seeing as the cycling of the action has no influence on this. Muzzle rise is caused by the exiting of gases behind the projectile, and the force created at the muzzle generates torque, flipping the muzzle upwards. Examples are bolt action rifles and revolvers; no cycling of an action, but there is still muzzle rise.
http://www.youtube.com/watch?v=B-jzkDviIwo
2. If the forces generated by the reciprocating mass over the bore have an effect, wouldn't they counteract muzzle rise, seeing as they are over the centerline, instead of under?
It's the same principle as placing the butt of the rifle low on the shoulder and as close to the center line of the body of the shooter as possible.
We are all aware of Newton's Law- for every action there is an equal and opposite reaction, and a body in motion will stay in motion.
The acceleration/deceleration vector of the piston & actuator rod located above the bore must angle towards the point of contact with the shooter. If it's above the bore, this angle is downward. This vector change is not inline with or parallel to the centerline of the bore and will cause displacement of the muzzle. The further from the centerline of bore, the greater the mass and/or velocity of the reciprocating parts, the greater the offset force to displace the muzzle
While the inline piston eliminates offset forces from the reciprocating mass, thrust and recoil, there are other factors that cause muzzle displacement, such as the stance of the shooter and location of the center of gravity, vertically and horizontally.
What this means is, it's easier to control the muzzle rise of an AR with it's design vectoring the forces of of recoil, thrust and inertia inline and parallel with the bore and bolt straight back into the shoulder of the shooter than it is with a design that has offset forces coming from a second angle
2. If the forces generated by the reciprocating mass over the bore have an effect, wouldn't they counteract muzzle rise, seeing as they are over the centerline, instead of under?
Weight can help reduce muzzle rise unless that weight is moving, a revolver vs. an automatic pistol is a great example. The Kriss .45 ACP submachinegun is an example of using that moving weight to counter rise.
This vector change is not inline with or parallel to the centerline of the bore and will cause displacement of the muzzle. The further from the centerline of bore, the greater the mass and/or velocity of the reciprocating parts, the greater the offset force to displace the muzzle
It is not the the boreline, but the force vectors around the center of gravity. If you add 20 pounds of lead to the carrying handle of an AR recoil will rotate the tip of the barrel down. That means the DI "inline piston" is not torsion free unless the CG is in the barrel line. Even if it were, adding a 2 pound scope on top of the rifle would move CG up enough to turn the tables to favour a piston. (Btw. I find talking about pistons in DI confusing. Sure, it has one, but so what? I mean steam engine has piston in it, but if I say "piston engine" people do not think I am talking about steam engines for sure.)
Adding to that, the moving parts of a AR piston are mere percents of the rifles overall weight of the weapon system we can safely say that their effect on overall recoil is very, very small.
I believe it is more about tuning the gun than choosing a operating system. Piston will give more vibration to the gun due to parts moving about, but that is about it. DI will be smoother in that sense as well as by the fact the force to the BCG is delivered by compressible (read: soft) gas rather than solid steel.
Actual recoil is the same, perceived recoil can be quite a bit different. If we can talk about .223 having recoil in the first place.
It is not the the boreline, but the force vectors around the center of gravity. If you add 20 pounds of lead to the carrying handle of an AR recoil will rotate the tip of the barrel down. That means the DI "inline piston" is not torsion free unless the CG is in the barrel line. Even if it were, adding a 2 pound scope on top of the rifle would move CG up enough to turn the tables to favour a piston. (Btw. I find talking about pistons in DI confusing. Sure, it has one, but so what? I mean steam engine has piston in it, but if I say "piston engine" people do not think I am talking about steam engines for sure.)
Adding to that, the moving parts of a AR piston are mere percents of the rifles overall weight of the weapon system we can safely say that their effect on overall recoil is very, very small.
I believe it is more about tuning the gun than choosing a operating system. Piston will give more vibration to the gun due to parts moving about, but that is about it. DI will be smoother in that sense as well as by the fact the force to the BCG is delivered by compressible (read: soft) gas rather than solid steel.
Actual recoil is the same, perceived recoil can be quite a bit different. If we can talk about .223 having recoil in the first place.
That's a great way to think about it, the CG and overall tune of the weapon.
Jippo, I ask your patience and understanding as I struggle to share a technical discussion with you through cultural differences and language barriers
It is not the the boreline, but the force vectors around the center of gravity.
It is about the boreline because in the AR, thrust, recoil and reciprocating mass all line up through to the shooter's shoulder.
If you add 20 pounds of lead to the carrying handle of an AR recoil will rotate the tip of the barrel down. That means the DI "inline piston" is not torsion free unless the CG is in the barrel line. Even if it were, adding a 2 pound scope on top of the rifle would move CG up enough to turn the tables to favour a piston.
The problem with this theory is it does not take into consideration the contact point with the shooter. With the reciprocating mass above the bore of the AR, it is above where the buttstock contacts with the shooter. It's also important to remember that contact with the shooter changes the center of gravity of the mass affected by the recoil forces.
Simply adding 20 lbs of mass will reduce recoil to the shooter simply because there is more moment to over come. But the vector of that moving mass will angle from it's center of gravity down to where the rifle contacts the shooter causing an upward displacement of the muzzle.
(Btw. I find talking about pistons in DI confusing. Sure, it has one, but so what? I mean steam engine has piston in it, but if I say "piston engine" people do not think I am talking about steam engines for sure.)
There are also folks that call magazines "clips".
First, not all steam engines have pistons. Some steam engines are turbines. Not all reciprocating piston engines use internal combustion. Second, it states in the patent that "This invention is a true expanding gas system instead of the conventional impinging gas system."
It is important to understand that the AR has a piston, why it was place as it was and what happens when it's relocated.
As this is a technical thread to discuss how the AR actually works and why, it's important to clearly define what is being discussed.
I am not intimately familiar with the AK system, but isn't the piston a part of the carrier? Or is it a op-rod that is tapped by a separate piston inside the gas block? If the piston, op-rod and carrier are integrated, the AK is, by definition of the gases acting directly on the carrier, also a direct impingement system.
Adding to that, the moving parts of a AR piston are mere percents of the rifles overall weight of the weapon system we can safely say that their effect on overall recoil is very, very small.
Just what is the mass of the moving parts in comparison to the rest of the rifle? Don't forget the momentum of the moving parts also increasing how much energy they have. A 5.56 bullet only weighs about 69 grains, but it's velocity gives it an affect on the target much greater than it weight alone. Do not forget leverage. The further the reciprocating mass is from the center line of the bore (and where the rifle comes in contact with the shooter) the greater the leverage it has.
I believe it is more about tuning the gun than choosing a operating system.
Choosing the operating system is an important step in tuning the rifle as it determines the basics of how recoil forces are handled mechanically and what steps in the tuning process will work. With the inline piston, tuning starts by placing all the vectors of thrust, recoil and reciprocating mass parallel and centered to each other.
I agree that any rifle will work better when tuned, but what you start with is important as to what kind of tuning it will respond to.
Piston will give more vibration to the gun due to parts moving about, but that is about it.
This is another reason why it's important to clarify the fact the AR has a piston. The idea that adding a piston to an operating adds to vibration under recoil isn't accurate. The piston of the AR is very short and stiff, vibrations will be high frequency and flex minimal.
If you study slow motion footage of a ComBloc AK during firing, you will see how it flexes like a noodle. With the top cover removed, you can see the long rod on the carrier flexing like crazy. Vibration is of a much lower frequency. Unless the vibrations are tuned to cancel each other out, they only increase the force needed to control muzzle displacement.
DI will be smoother in that sense as well as by the fact the force to the BCG is delivered by compressible (read: soft) gas rather than solid steel.
Actual recoil is the same, perceived recoil can be quite a bit different. If we can talk about .223 having recoil in the first place.
Again, the fact that the amount of recoil energy generated is the same regardless of operating system has been covered many times.
Please understand that the inline piston system brings these forces inline with the bore. It does not eliminate all muzzle climb as there are other factors to consider.
With the recoil forces unified, it makes it easier to tune the rest of the rifle and the stance of the shooter to control muzzle displacement.
Remember- TANSTAAFL. There Ain't No Such Thing As A Free Lunch. Whether it's an inline piston (or as rob_s called it "internal piston), offset piston, delayed roller lock, blow back, bolt action- whatever, every design has it's compromises.
Of all the different centerfire rifles I've shot, the AR is one of the easiest to control muzzle displacement. Part of that is due to caliber, but it's inline piston design and ergonomics also play a large part
It is about the boreline because in the AR, thrust, recoil and reciprocating mass all line up through to the shooter's shoulder.
This sort of nullifies the whole discussion and proves the point I am making.
If piston moves the CG of the BCG up half an inch, then moving the buttplate up half an inch more than counters that. Why, because it is far from the CG of the gun with lots of leverage causing more torque.
What you are saying is that the design of buttstock is more important than the operating system. We agree, and that was the whole point I was making. In extreme case one could put optics on a very elevated mount and turn a buttstock upside down to create a support point high above the barrel and downward recoil impulse. That is weapon ergonomics design and a seperate issue of operating system.
The miniscule difference we are talking about is all but lost in the other parameters of the weapon system, nevermind the stance of the shooter. Difference between two persons who shoot with the buttplate in different position on their body will cause the weapon behave much differently than a change in the operating system ever could
The problem with this theory is it does not take into consideration the contact point with the shooter.
That varies by the shooter, making it kind of hard to consider.
Simply adding 20 lbs of mass will reduce recoil to the shooter simply because there is more moment to over come. But the vector of that moving mass will angle from it's center of gravity down to where the rifle contacts the shooter causing an upward displacement of the muzzle.
Think about the thrusters used to rotate the Apollo mission modules in space, this is exactly the same thing.
If the piston, op-rod and carrier are integrated, the AK is, by definition of the gases acting directly on the carrier, also a direct impingement system.
Good luck re-defining a long stroke piston system.
Just what is the mass of the moving parts in comparison to the rest of the rifle? Don't forget the momentum of the moving parts also increasing how much energy they have. A 5.56 bullet only weighs about 69 grains, but it's velocity gives it an affect on the target much greater than it weight alone. Do not forget leverage. The further the reciprocating mass is from the center line of the bore (and where the rifle comes in contact with the shooter) the greater the leverage it has.
All the energy is coming from the cartridge propellant, also that few percent that is used to reload the gun. It could be argued that the heavier BCG reduces the recoil because it needs more energy to operate. So infact heavier BCG reduces recoil because we get less output from the muzzle. Regardless, do you really think it is import?
The location where the force is applied is hardly relevant as it only torsions the BCG near the CG. If it were important we would only have piston designs were the piston is under the barrel to eliminate muzzle rise.
This is another reason why it's important to clarify the fact the AR has a piston. The idea that adding a piston to an operating adds to vibration under recoil isn't accurate. The piston of the AR is very short and stiff, vibrations will be high frequency and flex minimal.
Piston system on my AR is as long as in my AK and much thinner. My piston AR shoots sub-moa and my AK isn't much worse even without freefloating the pencil barrel it has got.
If you study slow motion footage of a ComBloc AK during firing, you will see how it flexes like a noodle. With the top cover removed, you can see the long rod on the carrier flexing like crazy. Vibration is of a much lower frequency. Unless the vibrations are tuned to cancel each other out, they only increase the force needed to control muzzle displacement.
Gas piston on an AK is attached to the carrier via a roll pin that acts as an axle for the piston pivot around. If the design was "one piece" solid, it would exert pressure to the barrel which would diminish accuracy and move the POI around when the weapon warms up. So it is supposed to be loose and vibrate.
And no these vibrations do not cause the muzzle to rise anywhere, they just add, well, vibration to the recoil.
Of all the different centerfire rifles I've shot, the AR is one of the easiest to control muzzle displacement. Part of that is due to caliber, but it's inline piston design and ergonomics also play a large part
There is a reason AR dominates the 3-gun & rifle IPSC scene.
sinlessorrow
03-26-12, 15:42
Here is how to "piston" in the AR-15 works
Photos courtesy of BigBore of ADCO
http://www.adcofirearms.com/junkpics/thisisapiston.jpg
http://www.adcofirearms.com/junkpics/cylinderview.jpg
http://www.adcofirearms.com/junkpics/locked-un.jpg
http://www.adcofirearms.com/junkpics/gaschamber.jpg
Pictures are always easier than words.
It should be noted that despite carbon build up the M4 maintained a 3,600MRBS in OIF and OEF.
militarymoron
03-26-12, 16:05
The location where the force is applied is hardly relevant as it only torsions the BCG near the CG. If it were important we would only have piston designs were the piston is under the barrel to eliminate muzzle rise.
all else being equal (stock design, c.g. of the rifle etc), i do think it's relevant. if i understand it correctly, the amount of perpendicular offset of a reciprocating mass from the axis of travel is going to affect the moment of inertia (parallel axis theorem for mass moment of inertia), and in turn, the amount of movement the rifle moves off axis (reacts) during the reciprocating cycle. it should return to the same spot, but move further off it during the cycle. this is not to be confused with the reaction of the rifle to the bullet leaving it.
Relevance depends on the usage. I'm sure that a competition shooter, everything on the gun exept the operating system being identical, could shave off a hundredth of a second here and another one there with a DI. Be it the vibrations, muzzle flip, what ever. When every hundredth of a second counts it becomes relevant. That is why DI rifles tend to be popular with competition shooters.
Soldier or police officer might appreciate other things more than those occasional fractions of a second. That is why some of them wield H&K's, and none of them JP racers with low mass carriers.
Relevance is a bit of a personal issue here.
militarymoron
03-26-12, 16:33
i'm keeping the relevance technical, not based on personal preference or use. the question was whether a piston gun might add more to the movement off axis than a DI gun. it's either 'yes' or 'no'. whether it makes a practical difference to the particular user is a different question.
sinlessorrow
03-26-12, 16:46
Relevance depends on the usage. I'm sure that a competition shooter, everything on the gun exept the operating system being identical, could shave off a hundredth of a second here and another one there with a DI. Be it the vibrations, muzzle flip, what ever. When every hundredth of a second counts it becomes relevant. That is why DI rifles tend to be popular with competition shooters.
Soldier or police officer might appreciate other things more than those occasional fractions of a second. That is why some of them wield H&K's, and none of them JP racers with low mass carriers.
Relevance is a bit of a personal issue here.
What other things might they appreciate more?
all else being equal (stock design, c.g. of the rifle etc), i do think it's relevant. if i understand it correctly, the amount of perpendicular offset of a reciprocating mass from the axis of travel is going to affect the moment of inertia (parallel axis theorem for mass moment of inertia), and in turn, the amount of movement the rifle moves off axis (reacts) during the reciprocating cycle. it should return to the same spot, but move further off it during the cycle. this is not to be confused with the reaction of the rifle to the bullet leaving it.
Yes! Thank you. And once the rifle is in motion from the recoil, it's easier for the offset force vectors to displace the muzzle
i'm keeping the relevance technical, not based on personal preference or use. the question was whether a piston gun might add more to the movement off axis than a DI gun. it's either 'yes' or 'no'. whether it makes a practical difference to the particular user is a different question.
Again, yes. I am looking at this strictly from a technical point of view. Whether or not the difference important is up to each individual
What other things might they appreciate more?
Whether or not the weapon fits the needs of the mission at hand, including but not limited to, operator familiarity
i'm keeping the relevance technical, not based on personal preference or use. the question was whether a piston gun might add more to the movement off axis than a DI gun. it's either 'yes' or 'no'. whether it makes a practical difference to the particular user is a different question.
I think already that was covered very early on in the discussion. Any moving component will add to the vibrations of the gun, especially so if such a part is not tuned not to hitbackstops etc.
What other things might they appreciate more?
You should ask them about that. When you realise DI AR is not necessarily the end of all military weapon design you might be closer to enlightment.
Or maybe they are just smart enough not to take an Indycar off-roading.
sinlessorrow
03-26-12, 23:08
I think already that was covered very early on in the discussion. Any moving component will add to the vibrations of the gun, especially so if such a part is not tuned not to hitbackstops etc.
You should ask them about that. When you realise DI AR is not necessarily the end of all military weapon design you might be closer to enlightment.
Or maybe they are just smart enough not to take an Indycar off-roading.
i realize the Stoner system is not the be all end all, then again no rifle is. so far we have not reached perfection, and newer rifles only offer a very minute upgrade, certainly not enough to replace the Stoner System that works very well.
that said the so called "indycar" seems to do just fine off roading in iraq and afghanistan. during OEF and OIF it maintained a 3,600MRBS
that said the so called "indycar" seems to do just fine off roading in iraq and afghanistan. during OEF and OIF it maintained a 3,600MRBS
So which military formation has used "JP racers with low mass carriers" in OEF or OIF?
Because that is what the "Indycar" was referring to.
sinlessorrow
03-27-12, 12:18
So which military formation has used "JP racers with low mass carriers" in OEF or OIF?
Because that is what the "Indycar" was referring to.
I get what you are saying now, there was just a miss-communication on my end.
The muzzle brake has a lot to do with that.
If you take off the brake it has more muzzle rize, just like if you add a brake to an AR-15 you will have absolutely no muzzle rise, the diff is one has a ton of flash the other doesnt
Perhaps at night time, but the flash signititure is not noticeable at all during day time when I've fired them.
This is frustrating. This has been explained over and over again.
The amount of recoil energy a cartridge generates remains the same regardless of action type it's fired in, whether it's semi-auto, full-auto, bolt action, pump action, revolver- what have you. It's not subjective, opinion, dependent on the phase of the moon or how you scatter chicken blood. It's physics, nothing more
The only changes to recoil energy the design of the action and ergonomics can make is how it affects the weapon and the shooter by changing the time and vector of the recoil energy distribution
Did I say the recoil energy wasn't the same? What should I say then?
Did I say the recoil energy wasn't the same? What should I say then?
Your statement was "Rifles with conventional operating rods having more recoil when compared to AR15's is mostly subjective".
The way it's worded, it sounds like what you are saying is that whether one system or the other has more recoil is subjective. It is not. It's a known. Two different eight pound rifles firing the same cartridge will have the same amount of recoil. What is subjective is how the recoil feels to the shooter
Your statement was "Rifles with conventional operating rods having more recoil when compared to AR15's is mostly subjective".
The way it's worded, it sounds like what you are saying is that whether one system or the other has more recoil is subjective. It is not. It's a known. Two different eight pound rifles firing the same cartridge will have the same amount of recoil. What is subjective is how the recoil feels to the shooter
That's what I meant.
This sort of nullifies the whole discussion and proves the point I am making.
If piston moves the CG of the BCG up half an inch, then moving the buttplate up half an inch more than counters that. Why, because it is far from the CG of the gun with lots of leverage causing more torque.
Moving the piston to above the bore does change the CG but by a very minute amount. More importantly, it changes the location of reciprocating mass. Motionless, the change has very little affect. But as it accelerates back and forth in it's race, it affect becomes much greater.
(While I have talked about muzzle rise, what it's really about is muzzle displacement, whether it's up, down, left or right)
What you are saying is that the design of buttstock is more important than the operating system. We agree, and that was the whole point I was making. In extreme case one could put optics on a very elevated mount and turn a buttstock upside down to create a support point high above the barrel and downward recoil impulse. That is weapon ergonomics design and a seperate issue of operating system.
Yes, ergonomics of the rifle (including the design of the buttstock) are very important when it comes to controlling recoil and muzzle displacement. However, a high scope mount, although it's fixed and does does not reciprocate, will affect recoil vector by placing a mass above the point where the rifle contacts the shooter, especially if it's heavy (if it's very light and rigid, it will have little affect either way).
The miniscule difference we are talking about is all but lost in the other parameters of the weapon system, nevermind the stance of the shooter. Difference between two persons who shoot with the buttplate in different position on their body will cause the weapon behave much differently than a change in the operating system ever could
Agreed, shooter's stance goes a long way to controlling recoil and muzzle displacement. But offset recoil forces that add to muzzle displacement means stance is even more critical for control.
Another aspect we haven't talked about is shooter fatigue. "Ounces are pounds; pounds are pain". If a rifle has more inherent muzzle displacement, whether through offset recoil forces or ergonomic design, that's more work for the shooter to control. For a few shots, no big deal. But it all adds over time. Battles are determined by resource management. The side that runs out of critical resources first, loses. Less effort to control the rifle means less shooter fatigue which is a good thing.
Think about the thrusters used to rotate the Apollo mission modules in space, this is exactly the same thing.
Yes, it is. Inline thrust/recoil pushes the rocket in a straight line along it's path. Offset forces are used to change pitch, yaw and roll.
Good luck re-defining a long stroke piston system.
Not trying to change it's definition. Just pointing out how a certain definition could be applied
All the energy is coming from the cartridge propellant, also that few percent that is used to reload the gun. It could be argued that the heavier BCG reduces the recoil because it needs more energy to operate. So infact heavier BCG reduces recoil because we get less output from the muzzle.
Energy cannot be destroyed. The amount of work each cartridge generates is the same regardless of what weapon it's fired in. Yes, the BCG is operated by siphoning off energy from the cartridge, but that energy isn't "used up" it's simply stored someplace else until used. In this case, the energy is used to accelerate a reciprocating mass and those acceleration forces are going to affect the rifle.
Using the energy to operate the BCG doesn't reduce overall recoil, it changes the duration and direction. Because of how the energy is used, that portion is delayed and direction is changed. Recoil may feel softer, but the amount of energy remains the same. Some energy is lost through heat and friction (which converts energy to heat) but that's energy lost or managed through inefficiency, not a reduction of energy
Regardless, do you really think it is import?
For the purposes of this discussion and to understand how and why things work, yes. If we didn't strive to understand the basic principles at work, we.d still be throwing rocks.
Maybe it's not important to the trigger puller, but just because a trigger puller doesn't find it important, doesn't mean it's not.
The location where the force is applied is hardly relevant as it only torsions the BCG near the CG. If it were important we would only have piston designs were the piston is under the barrel to eliminate muzzle rise.
If we simply placed the piston & actuator rod below the barrel, we'd have to change magazine location or route the actuator rod to one side or the other as was done with the Garand and M14. placing the offset forces below the barrel only changes their vector and the direction they try to displace the muzzle. A downward muzzle displacement is still a muzzle displacement.
The torsion does not only affect the BCG. The affect the entire rifle, even if only in some small way.
Piston system on my AR is as long as in my AK and much thinner. My piston AR shoots sub-moa and my AK isn't much worse even without freefloating the pencil barrel it has got.
Understanding how each system works and honestly assessing their strengths and weaknesses is not the same as saying "This gun good! This gun bad!"
Gas piston on an AK is attached to the carrier via a roll pin that acts as an axle for the piston pivot around. If the design was "one piece" solid, it would exert pressure to the barrel which would diminish accuracy and move the POI around when the weapon warms up. So it is supposed to be loose and vibrate.
And no these vibrations do not cause the muzzle to rise anywhere, they just add, well, vibration to the recoil.
Vibration is motion and motion is displacement. It can be damped or two forces used to cancel each other out. If you study slow motion footage of a combloc AK being fired, you will see the muzzle dancing from barrel flex (vibration). Although it is muzzle displacement it's not exactly what we were discussing when talking about muzzle displacement from recoil.
If the barrel flex is the barrel flex is the same every time and the rifle accurate shot after shot, it's not a worry.
I do hope to get a chance to study the AK more closely and thanks for explaining about the piston & carrier.
There is a reason AR dominates the 3-gun & rifle IPSC scene.
3-Gun and IPSC takes the basics of the AR and pushes them to a tightly focused and narrow extreme. If the foundation of the AR wasn't sound, they would start with something else.
ARs dominate in other areas as well.
I told my brother that I've gained a much better understanding of the AR. He told me I would have had an even better one if I'd joined the Army. I was thinking of all the AR myths circulating throughout our military when he said "There's a lot you learn about a rifle when you live with it". True words, whether it's an AR, AK or other rifle
Interesting discussion, and I regret not studying physics more in school.
@Mistwolf:
You speak of the reciprocating mass of the offset piston and op rod, and state that this acceleration of mass causes increasing muzzle rise.
Is there a way of calculating the actual effect of this, and compare it to an inline piston/DI system? The piston and oprod of an HK416 weighs 119 grams, moves maybe an inch during cycling and is located 2,2cm over the centerline of the bore. Don't know the velocity....
I know you state it, but numbers prove the point better.
Also, as far as I understand it, the whole issue of muzzle rise is a result of torque, correct?
Torque is calculated by using the perpendicular distance between the center mass of the weapon below the bore axis, the force on the gun due to expanding gases, and the inertia of the gun around it's center mass.
Does the reciprocating mass of the piston and oprod affect the generated torque (doesn't seem like it to me), or does it change the center of gravity at all?
What I have a hard time wrapping my head around is that the minimal weight of the piston and rod, moving such a short distance in a very short time can overcome the recoil forces already acting on the weapon, and change the vector of those recoil forces. It also seems to me that the muzzle rise is a result of something other than reciprocating mass.
Not arguing to argue, but trying to learn something.
That's what I meant.
My apologies for misunderstanding
Interesting discussion, and I regret not studying physics more in school.
@Mistwolf:
You speak of the reciprocating mass of the offset piston and op rod, and state that this acceleration of mass causes increasing muzzle rise.
Is there a way of calculating the actual effect of this, and compare it to an inline piston/DI system? The piston and oprod of an HK416 weighs 119 grams, moves maybe an inch during cycling and is located 2,2cm over the centerline of the bore. Don't know the velocity....
I know you state it, but numbers prove the point better.
Also, as far as I understand it, the whole issue of muzzle rise is a result of torque, correct?
Torque is calculated by using the perpendicular distance between the center mass of the weapon below the bore axis, the force on the gun due to expanding gases, and the inertia of the gun around it's center mass.
Does the reciprocating mass of the piston and oprod affect the generated torque (doesn't seem like it to me), or does it change the center of gravity at all?
What I have a hard time wrapping my head around is that the minimal weight of the piston and rod, moving such a short distance in a very short time can overcome the recoil forces already acting on the weapon, and change the vector of those recoil forces. It also seems to me that the muzzle rise is a result of something other than reciprocating mass.
Not arguing to argue, but trying to learn something.
You make good points, especially about wishing I'd studied more. Yes, all of these forces we're talking about can be calculated. My math is inadequate to do so.
The reciprocating mass doesn't overcome the recoil vector, it adds to it. That is, it changes the angles at which the forces act. Small changes can be increased by leverage, velocity, acceleration and changing mass.
Yes, muzzle displacement does result from other factors such as the fulcrum point where the rifle rests against the shooter and the pivot points of the shooter's body.
An object at rest has a single, central center of gravity. When placed in motion, there is a dynamic CG which can change when acceleration and velocity vectors change.
Simple shapes such as a cube or sphere have basically one CG located in the center of it's mass.
A complex shape can have several CGs. Think of a bar with a sphere of equal diameter and mass at each end. The assembly will have a central CG between the spheres. In addition, each sphere and the bar will have their own CG. Put this assembly in motion, changing speeds and directions and the there will be a noticeable shift in it's dynamic CG. In general, the dynamic CG shifts towards the an accelerating force. The greater the acceleration, the greater the force
militarymoron
03-27-12, 17:39
Does the reciprocating mass of the piston and oprod affect the generated torque (doesn't seem like it to me), or does it change the center of gravity at all?
ask yourself first - how could it not affect the torque? if you move a mass inside an object, the c.g. changes; just like if you walk from the front of an airplane to the back, and to the front again, the c.g. of the plane will change.
if the c.g. changes, then any external forces acting on the object will have a different effect on that object.
Suwannee Tim
03-27-12, 20:51
Here is how I visualize recoil: MV is momentum, the product of mass and velocity. Momentum is conserved, this is a fundamental law of physics which extends down to the quantum level and up to the cosmological level. In a firearm, the sum of the MVs in the forward direction (bullet and powder gasses) equals the sum of the MVs in the rearward direction. If you have a recoiling mass in the rifle this moving mass quickly absorbs some of the MV then slowly delivering it back through the spring or impact as it comes to rest. The rub in all of this is that a shotgun like a recoil operated Browning Automatic with a large recoiling mass ought to kick less than, say a pump shotgun. Fact is the Browning has a reputation for being a hard kicking gun. The point is the perception of recoil is not as simple as the physics would indicate.
First I have to apologize, but I am starting to loose the track of the argument here.
I believe the situation is as follows:
1. People claim that piston AR has more recoil than DI AR.
2. People claim that piston AR torsions the rifle in a direction.
I see it like this:
1. This is untrue. Recoil comes from the cartridge putting a bullet traveling in to the direction of target and is dependant on the kinetic energy of bullet and gases exiting the muzzle in direction of the target. Recoil energy is roughly put the same (per Newton) as the combined kinetic energy of the bullet and the gases. On weapon systems that use the combustion energy of the cartridge to load a cartridge few percent of that energy is used to load the cartridge resulting in lower kinetic energy in both output from the muzzle and recoil. That means that a bolt action will have more recoil force than a semi-auto system. The is some variation between autoloaders as well, but this is not directly related to the issue of piston or not, but to the amount and pressure of the gases used to operate the loading mechanism, that is gas port size and time it is operating the system.
2. This is true. Of the few percent of the energy used to load the cartridge some is used to move parts that are offset from the CG of the weapon. But saying that DI hasn't got this phenomen is incorrect as well, depending on the CG of the gun. But the thing here is that in all cases AR these parts are close to the CG and the forces used to operate them are mere fractions of the overall recoil energy. Added to that, these fractions are used to move parts in direction of the overall recoil force, not perpendicular to it, meaning that their effect to muzzle displacement can not be very large at all. In same fashion somebody could make an argument that DI causes muzzle displacement as it wents gas to right from the BCG causing the rifle recoil left (again per Newton). I mean, sure it does, but is it relevant?
What is important and what not in recoil.
If recoil is a single push that moves gun in a given direction every shot it can be countered and reduced to a simple push rearwards with no sideways component. Two keys to this are weapon design and stance, with most important being the latter. Shooter weighs considerably more than his rifle and the way he places the buttstock on his body and utilises his hands has a very profound effect on how the rifle will act in recoil. Weapon ergonomic design makes it only easier. Buttstock desing is IMHO the most important component, then muzzle device, then things related to the BCG. Of the things related to the BCG the most important is the tuning/adjustment of gas and action springs to prevent BCG from "bottoming out" whilst maintaining reliability. Low mass carriers and such IMHO mostly reduce the vibration part as they allow the energy released when the bolt slams close again to be smaller.
In any case IMHO things related to type of the BCG come very low in my list of recoil priorities. Even then, I think the game is between reliability and recoil vibrations. If one uses low mass BCG, reduced gas pressure, lighter action spring etc., one is also reducing the amount of excess energy used in reloading the weapon. Less there is "over" gassing less there is room for external variables that might cause a malfunction. Just that. In this aspect IMHO selection between piston or DI is quite unimportant, unless the gun is used for competitions and the shooter wants to really minimise all the possible vibrations.
About the tuning of the gun
If you already haven't watched this video, do it now:
http://www.youtube.com/watch?feature=player_embedded&v=bt41wNmau_8
In it you will find three guns in side by side comparison slow speed video. The piston gun in the middle exhibits the least amount of vibrations of the three just because it is tuned. It doesn't have bolt bounce nor does it have buffer bottoming out. One needs to tune the gun as well as middle gun in the video to even notice offset forces on the BCG (if that is at all possible to do). Carrier slamming to the rear or BCG slamming close twice are far bigger shocks to cope with.
This discussion shouldn't be reduced to DI less recoil and no vibration but piston design has. It is not true.
sinlessorrow
03-28-12, 02:21
Jippo, that video shows that both piston guns have more muzzle flip than the DI rifle.
the HK seems to have even more than the bottom piston rifle
Jippo, that video shows that both piston guns have more muzzle flip than the DI rifle.
the HK seems to have even more than the bottom piston rifle
Did you read the disclaimer posted in the video description:
It is important to note that different shooters were behind each rifle - a gun blogger (not me), an airsoft guy, and an extremely heavy company rep. This has a big effect on recoil control as seen in the video.
Jippo, that video shows that both piston guns have more muzzle flip than the DI rifle.
the HK seems to have even more than the bottom piston rifle
As per my previous post, that is mostly dependant on the shooters stance. Claiming that piston has more recoil goes against Newtonian physics - if it were true all we know about physics is wrong.
Watch the BCG, watch the vibrations and how they affect the gun (concentrate on a single weapon at the time, you really need to look through it multiple times), that is the issue: tuning of the weapon. Piston in the center has less vibration than the piston in the bottom and the DI at the top. It is just simply tuned well: action spring, BCG weight and gas used are in sync.
To both MistWolf and Jippo, thank you for a very educational and informative discussion.
Just wished I had worded my disagreement with MistWolf's statement more accurately in my post, and said muzzle rise instead of recoil impulse.
I do not think the design differences, and the different physics, is the straw the breaks the camels back in terms of recoil management with either platform.
@militarymoron:
You are of course right, and I have no excuse for the absence of my brain when I asked the question....:suicide2:
It would seem quite logical, wouldn't it.
You make some very good points, Jippo
First I have to apologize, but I am starting to loose the track of the argument here.
I believe the situation is as follows:
1. People claim that piston AR has more recoil than DI AR.
2. People claim that piston AR torsions the rifle in a direction.
I see it like this:
1. This is untrue. Recoil comes from the cartridge putting a bullet traveling in to the direction of target and is dependant on the kinetic energy of bullet and gases exiting the muzzle in direction of the target. Recoil energy is roughly put the same (per Newton) as the combined kinetic energy of the bullet and the gases. On weapon systems that use the combustion energy of the cartridge to load a cartridge few percent of that energy is used to load the cartridge resulting in lower kinetic energy in both output from the muzzle and recoil. That means that a bolt action will have more recoil force than a semi-auto system. The is some variation between autoloaders as well, but this is not directly related to the issue of piston or not, but to the amount and pressure of the gases used to operate the loading mechanism, that is gas port size and time it is operating the system.
2. This is true. Of the few percent of the energy used to load the cartridge some is used to move parts that are offset from the CG of the weapon. But saying that DI hasn't got this phenomen is incorrect as well, depending on the CG of the gun. But the thing here is that in all cases AR these parts are close to the CG and the forces used to operate them are mere fractions of the overall recoil energy. Added to that, these fractions are used to move parts in direction of the overall recoil force, not perpendicular to it, meaning that their effect to muzzle displacement can not be very large at all. In same fashion somebody could make an argument that DI causes muzzle displacement as it wents gas to right from the BCG causing the rifle recoil left (again per Newton). I mean, sure it does, but is it relevant?
It is true that the inline piston system does not have less recoil than an offset piston. However, the same is true for every action type. An 8 lbs 5.56 rifle will have the same amount of recoil no matter what action it has. It's just that the self loading action temporarily divert some of the that energy as well as temporarily change it's direction. This delays part of the recoil from being transferred to the shooter. The same amount of recoil reaches the shooter, but it's over a longer period of time and feels softer. Think of it as having say, 5 lbs of ping pong balls poured over you versus having a 5 lbs lump of lead dropped from the same height.
The inline piston does not eliminate all muzzle displacement. There are other factors involved. But it does eliminate offset forces from recoil, thrust and reciprocating mass to reduce muzzle displacement.
What is important and what not in recoil.
If recoil is a single push that moves gun in a given direction every shot it can be countered and reduced to a simple push rearwards with no sideways component. Two keys to this are weapon design and stance, with most important being the latter. Shooter weighs considerably more than his rifle and the way he places the buttstock on his body and utilises his hands has a very profound effect on how the rifle will act in recoil. Weapon ergonomic design makes it only easier. Buttstock desing is IMHO the most important component, then muzzle device, then things related to the BCG. Of the things related to the BCG the most important is the tuning/adjustment of gas and action springs to prevent BCG from "bottoming out" whilst maintaining reliability. Low mass carriers and such IMHO mostly reduce the vibration part as they allow the energy released when the bolt slams close again to be smaller.
Agreed. It does little good to design an operating system for improved weapon control, then give the rifle poor ergonomics. I also share your opinion that ergonomics are more important to controlling muzzle displacement than a muzzle brake.
In any case IMHO things related to type of the BCG come very low in my list of recoil priorities. Even then, I think the game is between reliability and recoil vibrations. If one uses low mass BCG, reduced gas pressure, lighter action spring etc., one is also reducing the amount of excess energy used in reloading the weapon. Less there is "over" gassing less there is room for external variables that might cause a malfunction. Just that. In this aspect IMHO selection between piston or DI is quite unimportant, unless the gun is used for competitions and the shooter wants to really minimise all the possible vibrations.
This discussion is not about tuning any rifle within an inch of it's life for any kind of game. It's about exploring what the AR system really is. Tuning a rifle for softer recoil to the point it's reliability is at it's ragged edge isn't my thing. I agree that reliability takes priority over soft recoil
About the tuning of the gun
If you already haven't watched this video, do it now:
http://www.youtube.com/watch?feature=player_embedded&v=bt41wNmau_8
In it you will find three guns in side by side comparison slow speed video. The piston gun in the middle exhibits the least amount of vibrations of the three just because it is tuned. It doesn't have bolt bounce nor does it have buffer bottoming out. One needs to tune the gun as well as middle gun in the video to even notice offset forces on the BCG (if that is at all possible to do). Carrier slamming to the rear or BCG slamming close twice are far bigger shocks to cope with.
This discussion shouldn't be reduced to DI less recoil and no vibration but piston design has. It is not true.
It's not that the inline AR has no vibration or flex. It's only that the bolt and other parts are short and stiff so it's flex is minimal which has nothing to do with where the piston is located. The AR barrel still has enough flex that it affects tuning ammunition to match each individual rifle for maximum accuracy.
It's been an involved discussion. I'm not surprised anyone feels they are losing track. I am grateful to all participants that it's been civil as well as interesting and informative. Jippo, it's been stimulating
We can argue this until the cows come home and neither side will convince the other. The point is, both systems can be made to work.
When Eugene Stoner designed the so-called DI system (So-called because it is NOT the same as a true DI system as employed on the Llungman rifle) he did so because he was working to a "maximum weight with 20-rounds of ammunition" spec. Later, when he had the opportunity to design what he felt was the rifle that the military REALLY needed, he designed the AR18 with a piston.
Simply taking an AR and making it a piston-driven rifle by changing the gas key to a solid lump and adding a piston to push against it is inherently problematical because, unless you come up with a way to guide the bolt carrier, you end up with bolt tilt.
Piston systems do not eliminate fouling, they just move it to a different place.
DI systems do not, in and of themselves, cause rifles to fail due to heat or fouling. Just look at the Colt's video of the full-auto-to-destruction test of the M4 carbine. The rifle didn't fail because of the DI system, it failed at 535 rounds of continuous full auto fire because the barrel melted.
On the other hand I have some experience with a rifle with a piston system that is very similar to many of the ones being retrofitted to AR15s - the FAL. I personally have seen FALs with the gas piston so fouled that, after removal of the gas plug, you had to shotgun the rifle open, remove the bolt assembly and dust cover, and poke something into the gas piston hole in the receiver to push on the rear end of the gas piston to free it up so you could take the piston out to clean it.
In the end I think it comes down to these three points:
1. Buy what you want.
2. DI works just fine in an AR, and that's what I buy. I've yet to personally have any issue with my rifles in the usage that I give them that was a consequence of DI. But I'm buying on the tail end of 40+ years of a maturation process that DI has gone through, so I'd expect it to be reliable.
3. But if you want to have a piston AR, buy that instead. But be ready to accept the consequences if nothing is done to additionally guide the bolt carrier against the off-center thrust, and maybe you have to do a little R&D on the less-than-mature system to get the dwells, pressures, bolt velocity, etc. right.
Jippo, it's been stimulating
Indeed, thanks to you and everyone else taking part in the discussion. This is a very nice, informative forum. Lot's to learn in here.
sinlessorrow
03-28-12, 11:37
We can argue this until the cows come home and neither side will convince the other. The point is, both systems can be made to work.
When Eugene Stoner designed the so-called DI system (So-called because it is NOT the same as a true DI system as employed on the Llungman rifle) he did so because he was working to a "maximum weight with 20-rounds of ammunition" spec. Later, when he had the opportunity to design what he felt was the rifle that the military REALLY needed, he designed the AR18 with a piston.
Simply taking an AR and making it a piston-driven rifle by changing the gas key to a solid lump and adding a piston to push against it is inherently problematical because, unless you come up with a way to guide the bolt carrier, you end up with bolt tilt.
Piston systems do not eliminate fouling, they just move it to a different place.
DI systems do not, in and of themselves, cause rifles to fail due to heat or fouling. Just look at the Colt's video of the full-auto-to-destruction test of the M4 carbine. The rifle didn't fail because of the DI system, it failed at 535 rounds of continuous full auto fire because the barrel melted.
On the other hand I have some experience with a rifle with a piston system that is very similar to many of the ones being retrofitted to AR15s - the FAL. I personally have seen FALs with the gas piston so fouled that, after removal of the gas plug, you had to shotgun the rifle open, remove the bolt assembly and dust cover, and poke something into the gas piston hole in the receiver to push on the rear end of the gas piston to free it up so you could take the piston out to clean it.
In the end I think it comes down to these three points:
1. Buy what you want.
2. DI works just fine in an AR, and that's what I buy. I've yet to personally have any issue with my rifles in the usage that I give them that was a consequence of DI. But I'm buying on the tail end of 40+ years of a maturation process that DI has gone through, so I'd expect it to be reliable.
3. But if you want to have a piston AR, buy that instead. But be ready to accept the consequences if nothing is done to additionally guide the bolt carrier against the off-center thrust, and maybe you have to do a little R&D on the less-than-mature system to get the dwells, pressures, bolt velocity, etc. right.
I have to disagree with the Stoner part.
he designed the AR-16 after the rights to the AR-15 was sold to Colt. the AR-16 was eugenes final design at Armalite, who later went on to make the AR-18.
Eugenes final designs though where the KAC 7.62 rifles which are also DI
We can argue this until the cows come home and neither side will convince the other. The point is, both systems can be made to work.
When Eugene Stoner designed the so-called DI system (So-called because it is NOT the same as a true DI system as employed on the Llungman rifle) he did so because he was working to a "maximum weight with 20-rounds of ammunition" spec. Later, when he had the opportunity to design what he felt was the rifle that the military REALLY needed, he designed the AR18 with a piston.
Simply taking an AR and making it a piston-driven rifle by changing the gas key to a solid lump and adding a piston to push against it is inherently problematical because, unless you come up with a way to guide the bolt carrier, you end up with bolt tilt.
Piston systems do not eliminate fouling, they just move it to a different place.
DI systems do not, in and of themselves, cause rifles to fail due to heat or fouling. Just look at the Colt's video of the full-auto-to-destruction test of the M4 carbine. The rifle didn't fail because of the DI system, it failed at 535 rounds of continuous full auto fire because the barrel melted.
On the other hand I have some experience with a rifle with a piston system that is very similar to many of the ones being retrofitted to AR15s - the FAL. I personally have seen FALs with the gas piston so fouled that, after removal of the gas plug, you had to shotgun the rifle open, remove the bolt assembly and dust cover, and poke something into the gas piston hole in the receiver to push on the rear end of the gas piston to free it up so you could take the piston out to clean it.
In the end I think it comes down to these three points:
1. Buy what you want.
2. DI works just fine in an AR, and that's what I buy. I've yet to personally have any issue with my rifles in the usage that I give them that was a consequence of DI. But I'm buying on the tail end of 40+ years of a maturation process that DI has gone through, so I'd expect it to be reliable.
3. But if you want to have a piston AR, buy that instead. But be ready to accept the consequences if nothing is done to additionally guide the bolt carrier against the off-center thrust, and maybe you have to do a little R&D on the less-than-mature system to get the dwells, pressures, bolt velocity, etc. right.
This discussion isn't about whether or not you should buy an inline piston or offset piston upper for the AR. It's a technical discussion about the design, how it works, why and what it does and does not do.
You make a good point about carbon fouling. In fact, I find cleaning serious carbon fouling from the gas block of the FAL more work than cleaning the BCG of a Stoner design AR
I have to disagree with the Stoner part.
he designed the AR-16 after the rights to the AR-15 was sold to Colt. the AR-16 was eugenes final design at Armalite, who later went on to make the AR-18.
Eugenes final designs though where the KAC 7.62 rifles which are also DI
I stand corrected, sir.
I was not aware of the AR16. So did Stoner go to the gas piston on the AR16 because he thought it was better, or did he do so because Armalite sold the rights to the design to Colt's?
One other thing to consider is how the gas is delivered.
We've covered that the overall level of gassing or total impulse is important.
What also matters is the time duration over which that impulse is delivered.
Quick, high force or slow, low force.
The main driver is dwell time or the time from when the bullet passes the gas port until it exits the muzzle.
One of the supposed benefits of external piston systems is the gas block can be near the muzzle.
This requires the total impulse to be delivered in a very short time producing very high forces.
One other thing to consider is how the gas is delivered.
We've covered that the overall level of gassing or total impulse is important.
What also matters is the time duration over which that impulse is delivered.
Quick, high force or slow, low force.
The main driver is dwell time or the time from when the bullet passes the gas port until it exits the muzzle.
One of the supposed benefits of external piston systems is the gas block can be near the muzzle.
This requires the total impulse to be delivered in a very short time producing very high forces.
Which can actually be a bad thing if it means that extraction of the fired case is attempted before the obturated case releases its grip on the chamber wall.
The short dwell at high force, combined with a still-obturated case, means that the extractor either slips over the cartridge rim or rips it off, leaving the fired case in the chamber.
Is there a way of calculating the actual effect of this, and compare it to an inline piston/DI system? The piston and oprod of an HK416 weighs 119 grams, moves maybe an inch during cycling and is located 2,2cm over the centerline of the bore. Don't know the velocity...
There is one very important factor here, that makes calculations way more difficult. In HK416 piston and op-rod stop their travel before BCG does and piston with op rod travel forward and come to full stop before BCG. This counteracts some of torque generated initially by rearward movement of piston and op-rod and split torque impulses in time. Actually this is why Mr. Dragunov decided to use spring loaded short stroke system in his "precision rifle" - to reduce muzzle rise by changing timing of moving parts and reduce mass of those parts. Later on Russians also constructed prototype assault rifle (competed against AN-94), that practically canceled recoil by meant of timing masses moving in different directions (but was even more complicated than AN-94).
Personally I do not think that in HK416, it's piston and op-rod that are very light and move very close to barrel line, muzzle rise is more than in in-line (DI) piston AR-15 due to different operation system. However sharper recoil impulse, that HK has (rifle was designed as 10" system for use in harsh conditions) makes it harder to control by some used to differently working rifles.
Personally I do not have this experience, but users that switched from KAC SR-16 to HK416 actually feel that HK is easier to control in full-auto fire (however this can be due to higher overall mass of HK416), so no easy answers here.
For me situation that AR15 pattern rifles (with patent protection expired long ago) are only military rifles with "DI" system, while all other use either short or long stroke "piston" system (even some AR15 patterned rifles) is some kind of a hint. When some "HSLD" units over the world adapt AR15 patterned weapon systems, it is due to it's vastly superior ergonomic and flexibility of configuration, not due to "DI" system. For military purposes AR15 patterned weapons have sufficient accuracy with either operating system.
Personally I do not think that in HK416, it's piston and op-rod that are very light and move very close to barrel line, muzzle rise is more than in in-line (DI) piston AR-15 due to different operation system. However sharper recoil impulse, that HK has (rifle was designed as 10" system for use in harsh conditions) makes it harder to control by some used to differently working rifles.
You make some good points Montrala. I just wanted to add to this one with some of my experiences with the MR308. I have the 20" barrel version which uses, interestingly enough, the same length gas system as the 16" variant does. I have very little experience with other AR10 pattern guns, but I do find the BCG of the MR very heavy and the action spring is pretty strong as well. I believe they did design a lot of excess into the system to assure reliability in all conditions.
Interestingly enough the rifle recoils very smoothly, much like a bolt action .308. Thus I was not very surprised when I saw the video comparison posted the first time. Also all the people that have fired the gun have very uniformly commented on the soft shooting action it has, many of them very experienced riflemen.
One other thing to consider is how the gas is delivered.
We've covered that the overall level of gassing or total impulse is important.
What also matters is the time duration over which that impulse is delivered.
Quick, high force or slow, low force.
The main driver is dwell time or the time from when the bullet passes the gas port until it exits the muzzle.
One of the supposed benefits of external piston systems is the gas block can be near the muzzle.
This requires the total impulse to be delivered in a very short time producing very high forces.
US Army research shows with the Garand and the M14, the bullet is several feet from the muzzle before the piston even begins moving. Considering the dwell time of the bullet going from the gas port to the muzzle is less than half a millisecond, I doubt it has much affect on the operation of the action at all. I believe venting time is the greatest influence. The fact that suppressor use increases venting time and increases BCG velocities supports this theory
US Army research shows with the Garand and the M14, the bullet is several feet from the muzzle before the piston even begins moving. Considering the dwell time of the bullet going from the gas port to the muzzle is less than half a millisecond, I doubt it has much affect on the operation of the action at all. I believe venting time is the greatest influence. The fact that suppressor use increases venting time and increases BCG velocities supports this theory
Yes, "blowdown" time does contribute to the total impulse.
Suppressors do extend this blowdown time, as does barrel length.
On modern designs, I don't believe blowdown is the greatest contributor.
Actual pressure traces would show this.
The Garand system gas port is very near the muzzle of a very long barrel using a very large piston at low pressure.
I wouldn't be surprised if it operated mostly on Blowdown.
Consider how much smaller the gas port is on a 16" carbine vs a 16" middy. Blowdown time is identical and dwell is reduced.
I see your point, Clint. I don't have the dwell chart with me at the moment, but the time difference between the carbine and the middie is very short. Is it long enough to make a difference? The gases will be slowed to subsonic speeds after passing through the gas port. This ensures teh bullet will be long gone before the gas reaches the BCG.
The overall blow down time from ignition until the system drops to atmospheric is the same with either the carbine or middy when both barrels are of the same length. But blow down time from the time the bullet passes the gas port until the system drops to atmospheric is longer with the carbine. I do not know how much longer.
I admit my "Blow Down Theory" is just a theory, but the affect a suppressor has supports it
Came across an informative video by Brownell's that explains how an AR works. The only error is claiming the gases move the bolt forward. They do not. Hope this helps explain things
http://www.brownells.com/.aspx/lid=11417/learn/?source=CJ
sinlessorrow
04-15-12, 22:14
Came across an informative video by Brownell's that explains how an AR works. The only error is claiming the gases move the bolt forward. They do not. Hope this helps explain things
http://www.brownells.com/.aspx/lid=11417/learn/?source=CJ
Goodfind, thats a very good video.
We can argue this until the cows come home and neither side will convince the other. The point is, both systems can be made to work.
When Eugene Stoner designed the so-called DI system (So-called because it is NOT the same as a true DI system as employed on the Llungman rifle) he did so because he was working to a "maximum weight with 20-rounds of ammunition" spec. Later, when he had the opportunity to design what he felt was the rifle that the military REALLY needed, he designed the AR18 with a piston.
Simply taking an AR and making it a piston-driven rifle by changing the gas key to a solid lump and adding a piston to push against it is inherently problematical because, unless you come up with a way to guide the bolt carrier, you end up with bolt tilt.
Piston systems do not eliminate fouling, they just move it to a different place.
DI systems do not, in and of themselves, cause rifles to fail due to heat or fouling. Just look at the Colt's video of the full-auto-to-destruction test of the M4 carbine. The rifle didn't fail because of the DI system, it failed at 535 rounds of continuous full auto fire because the barrel melted.
On the other hand I have some experience with a rifle with a piston system that is very similar to many of the ones being retrofitted to AR15s - the FAL. I personally have seen FALs with the gas piston so fouled that, after removal of the gas plug, you had to shotgun the rifle open, remove the bolt assembly and dust cover, and poke something into the gas piston hole in the receiver to push on the rear end of the gas piston to free it up so you could take the piston out to clean it.
In the end I think it comes down to these three points:
1. Buy what you want.
2. DI works just fine in an AR, and that's what I buy. I've yet to personally have any issue with my rifles in the usage that I give them that was a consequence of DI. But I'm buying on the tail end of 40+ years of a maturation process that DI has gone through, so I'd expect it to be reliable.
3. But if you want to have a piston AR, buy that instead. But be ready to accept the consequences if nothing is done to additionally guide the bolt carrier against the off-center thrust, and maybe you have to do a little R&D on the less-than-mature system to get the dwells, pressures, bolt velocity, etc. right.
Solid points. As a DI and Piston owner, I would agree.
I own one of LMT's piston carbines. I've put somewhere in the 12-15k rounds through it (mostly cheap russian ammo). The advantages I've noticed over my DI weapons are as follows:
- The LMT seems to be less picky about ammo than my DI weapons. I've noticed significantly less malfunctions with the lower powered steel cased ammo (Tula, Uly, or old Wolf). With the LMT piston, I can also mix brass and steel cased in a mag without having a case stick. My DI weapons will occasionally choke if I do the same.
- Less lubrication burn off (specifically using CLP). (although I don't shoot suppressed or auto). I've found Mobil 1 stays put on both systems.
- Slightly easier to clean. Less carbon to scrape (If you are one of those white glove types.)
The disadvantages I've seen to the system
- Carrier tilt. I lost a buffer retainer pin after the bolt carrier damaged the extension tube enough to spit the buffer retaining pin out. The pin landed in the FCG and locked up the weapon. An anti-tilt buffer solved that issue. I actually have pictures of this in the piston forums on AR15.com
- Like your FAL example, if I shoot the LMT enough without cleaning the piston system, it becomes increasingly difficult to pull the piston/plug assembly out. I shot over a case of Uly without cleaning (which is filthy ammo) and had to pull the piston plug out with the pliers on my Leatherman. Amazingly, the weapon was still cycling. I now spray a shot of CLP into the piston plug, before pulling it out.
- Some proprietary parts. The piston, gas block, barrel, and bolt carrier are unique to LMT.
Its a toss up to what I would select if I bought another AR. I do prefer the piston AR for high volume blasting due to the advantages above. However, I have no doubts that a DI AR will run just as well as a piston AR, given ample lubrication and high quality ammo.
sinlessorrow
11-02-12, 21:30
I know alot of times in the debate about how the DI system works alot seem to think the expanding gas pushes the bolt forward. This is false, I found this very good cut away that shows that there is no room for the bolt to be pushed forward in the extension. The cutaway also shows how the gas is sent behind the bolt and gives an idea of how the piston in the system works.
http://img593.imageshack.us/img593/9981/jody6.jpg
militarymoron
11-02-12, 22:38
I found this very good cut away that shows that there is no room for the bolt to be pushed forward in the extension.
if there wasn't any space there wouldn't be enough clearance for the bolt to rotate and lock into the barrel extension. it's not like a slip fit bushing. it's a pretty loose fit, and this allows front-back movement of the bolt when it's locked. this is what they're talking about - a minute amount of movement - smaller than you can see in that photo. i'm talking about a few thousandths of an inch.
Failure2Stop
11-02-12, 22:46
I know alot of times in the debate about how the DI system works alot seem to think the expanding gas pushes the bolt forward. This is false, I found this very good cut away that shows that there is no room for the bolt to be pushed forward in the extension. The cutaway also shows how the gas is sent behind the bolt and gives an idea of how the piston in the system works.
http://img593.imageshack.us/img593/9981/jody6.jpg
The system most certainly exerts force forward on the bolt.
Typos brought to you via Tapatalk and autocorrect.
sinlessorrow
11-02-12, 22:55
The system most certainly exerts force forward on the bolt.
Typos brought to you via Tapatalk and autocorrect.
There may be force put on the bolt from the rear but there will not be any movement forward of the bolt like alot seem to think when they bring up the expanding gases, I guess I could have explained that a bit better. Alot of times you see people mention that when the gas expands its puts forward pressure on the bolt pushing it forward and reducing stress on the bolt lugs. This is not true.
I also notice alot of times on bolts the front part of the bolt lugs will have finish wear, I would reckon this comes from the locking and unlocking of the bolt slightly rubbing against the barrel extension, correct me if I am wrong here?
There may be force put on the bolt from the rear but there will not be any movement forward of the bolt like alot seem to think when they bring up the expanding gases, I guess I could have explained that a bit better. Alot of times you see people mention that when the gas expands its puts forward pressure on the bolt pushing it forward and reducing stress on the bolt lugs. This is not true.
I also notice alot of times on bolts the front part of the bolt lugs will have finish wear, I would reckon this comes from the locking and unlocking of the bolt slightly rubbing against the barrel extension, correct me if I am wrong here?
Even if it doesnt move, there is pressure pushing foreward on the bolt. You have the force of the main propelent pushing back, and this pushing foreward(to a lesser extent). Some of the forces cancel reducing the overall value of the rearward force vector. This will reduce friction on the lugs. If a sled is on the ground and you lay on it, it doesnt move, but there is much more static friction to overcome, and after that there is still more friction. This will cause the sled to get a hole much quicker.
sinlessorrow
11-03-12, 00:27
Even if it doesnt move, there is pressure pushing foreward on the bolt. You have the force of the main propelent pushing back, and this pushing foreward(to a lesser extent). Some of the forces cancel reducing the overall value of the rearward force vector. This will reduce friction on the lugs. If a sled is on the ground and you lay on it, it doesnt move, but there is much more static friction to overcome, and after that there is still more friction. This will cause the sled to get a hole much quicker.
This is true, there is gas pushing the bolt forward but it does not "move" forward like is generally said.
Not only is there practically no room(maybe a thousands of an inch as MM said, though I am still doubtful that little bit would even make any difference.) and the rearward force from the chamber there is no way for the bolt to actually move forward.
In order for the gases to move the bolt forward, there must be greater pressure inside the BCG than inside the bore. Pressure inside the BCG will either be less than or equal to the pressure inside the bore. Never greater. The pressure inside the BCG cannot move the bolt forward. What happens is that the pressure inside the bore simply drops enough that it's no longer exerting back thrust
The cutaway also shows how the gas is sent behind the bolt and gives an idea of how the piston in the system works.
I disagree with the characterization of Stoner's design as a Piston system. Yes it does involve a stationary piston as stated in his patent, but the system does more closely resemble an impingement system. The gases still transfer their energy to the carrier, as with the DI example in the first post, stoner just moved this transfer to a different place that is in line with the barrel. In Stoner's design none of the energy is transferred to the piston, it goes to the carrier which simply drags the bolt along for the ride.
http://i8.photobucket.com/albums/a38/VMerquise/DIcomparison.jpg
They are not the same. Do not forget for every reaction, there is an equal and opposite reaction. Draw the arrow in the opposite direction of the thrust to the carrier and what will you find? In teh Ljungman system, it's the incoming gas. In the AR, it's the piston. Another significant difference is the AR uses an expansion chamber.
What is the difference between a piston & cylinder system where the piston moves or the cylinder moves?
Stoner himself wrote that his system is not a DI system. Was he wrong?
In teh Ljungman system, it's the incoming gas. In the AR, it's the piston.
... and behind the piston is more gas. The gas in both cases is trying to expand in ALL directions. As far as the transfer of force is concerned the piston is no different from the walls of the gas tube in either design, or the ground under a rocket.
sinlessorrow
11-03-12, 07:07
A piston is a component of reciprocating engines, reciprocating pumps, gas compressors and pneumatic cylinders, among other similar mechanisms. It is the moving component that is contained by a cylinder and is made gas-tight by piston rings.
Sounds like a piston to me.
Wow, can’t believe this thread resurfaced.
In thinking if piston systems, first think of internal combustion systems. The ignition of the gun powder, like the gas-air mixture, causes an expansion. The bullet (piston in an engine), is forced to move down the bore (cylinder). There is no connecting rod to the bullet, so the bullet continues onward until over come by other forces. The expanding gases exhaust into the gas port and out of the muzzle, much the same as in an engine via the exhaust valve.
The gas tube, gas key, and gas chamber inside the bolt carrier make up the other cylinder in this system. The gases expand in this ‘cylinder’ until enough force overcomes the inertia of the BCG-buffer, and the friction created by surface contact areas felt by the BCG-buffer. The bolt tail area would be considered a stationary piston.
The conception of this being a piston system, because the bolt acts like a piston, though initially stationary, and not a direct impingement is FALSE. Expanding gases are the actuating (impinging) force in this system, NOT THE BOLT! Even in the labeled ‘Piston system’ for the AR, the expanding gases STILL provide the impinging force for the motion of the BCG.
Both systems use an expanding gas to impart (impinge) a force to move a mechanical system after the mechanical system’s inertia is overcome. Only difference in the two AR systems would be the physical size of second ‘cylinder’, where and the impingement takes place, and where the gases are exhausted.
Sounds like a piston to me.
Yes, and BOTH the DI example and Stoner's design have these. Are they BOTH now Piston systems? No.
Wow, can’t believe this thread resurfaced.
Well I know how the crowd on this site likes to see we newbs doing our own research and leg work rather than posting annoying threads. I just wanted to weigh in on this as I felt calling Stoner's design a piston system was insulting to his achievement.
sinlessorrow
11-03-12, 10:14
Yes, and BOTH the DI example and Stoner's design have these. Are they BOTH now Piston systems? No.
Well I know how the crowd on this site likes to see we newbs doing our own research and leg work rather than posting annoying threads. I just wanted to weigh in on this as I felt calling Stoner's design a piston system was insulting to his achievement.
Why is calling the Stoner system a piston system an insult? The design basically is a piston system.
The bolt carrier is the gas chamber where the gas expands and pushes against the piston on the bolt that contains the gas rings.
Well I know how the crowd on this site likes to see we newbs doing our own research and leg work rather than posting annoying threads. I just wanted to weigh in on this as I felt calling Stoner's design a piston system was insulting to his achievement.
You did not resurrect this thread, but you obviously understand the misconception of how the AR system is perceived. I guess a lot of people actually think they build ARs as well.
sinlessorrow
11-03-12, 10:17
You did not resurrect this thread, but you obviously understand the misconception of how the AR system is perceived. I guess a lot of people actually think they build ARs as well.
So then what do people build?
Why is calling the Stoner system a piston system an insult? The design basically is a piston system. It ignores the fact that the force moving the system is the expanding gas by method of combustion.
The bolt carrier is the gas chamber where the gas expands and pushes against the piston on the bolt that contains the gas rings. The gas expands inside the BCG, and inside the gas key, and inside the gas tube.
... --- ...
The gas in both cases is trying to expand in ALL directions. As far as the transfer of force is concerned the piston is no different from the walls of the gas tube in either design, or the ground under a rocket.
This is true of a system with the piston located within the gas block as well
... and behind the piston is more gas.
Does this change the system from a piston system to a direct impingement system?
...The conception of this being a piston system, because the bolt acts like a piston, though initially stationary, and not a direct impingement is FALSE. Expanding gases are the actuating (impinging) force in this system, NOT THE BOLT! Even in the labeled ‘Piston system’ for the AR, the expanding gases STILL provide the impinging force for the motion of the BCG.
Both systems use an expanding gas to impart (impinge) a force to move a mechanical system after the mechanical system’s inertia is overcome. Only difference in the two AR systems would be the physical size of second ‘cylinder’, where and the impingement takes place, and where the gases are exhausted.
So what you are trying to tell me is that when Eugene Stoner, the designer of the gas system in this discussion wrote in the patent that this isn't a direct impingement system, he was wrong?
In the AK and FAL, the gases impinge directly on the piston which impinges directly on the carrier which drags the bolt along for the ride. Does that make this system a direct impingement system? I'll give you in both case neither bolt acts as a piston. Or does it make it an indirect impingement system with the piston acting as the go between?
In the case of the AK, is not the piston attached to the carrier? If so, isn't that the same thing as the Ljungman, just much longer? If it is, would not that make the AK a direct impingement system as well?
So then what do people build?
In the context of ARs, sans raw material and machinery, nothing.
So what you are trying to tell me is that when Eugene Stoner, the designer of the gas system in this discussion wrote in the patent that this isn't a direct impingement system, he was wrong?
Only in the same way that Edison was wrong if he ever said his incandescent bulb was not a torch.
So what you are trying to tell me is that when Eugene Stoner, the designer of the gas system in this discussion wrote in the patent that this isn't a direct impingement system, he was wrong?
He can call it anything he wants. It still does not diminish the fact that a redirected expanding gas impinges, imparts, strikes with a force on the surfaces of a closed system until something gives way.
sinlessorrow
11-03-12, 11:12
He can call it anything he wants. It still does not diminish the fact that a redirected expanding gas impinges, imparts, strikes with a force on the surfaces of a closed system until something gives way.
Then what rifles actually use a piston system?
In the context of ARs, sans raw material and machinery, nothing.
Have you built a wall or fence? Or is that just assembling too, since you can get fence posts, bricks, and other materials?
Then what rifles actually use a piston system?
In the very same way you could say the Ljungman DI system uses a piston. It does (the carrier that moves because of the gas pressure).
I can come up with exactly two ways (not saying there aren't other...) of converting pressure in to mechanical action: piston and turbine.
What you are arguing is semantics, not mechanics. I speak as a non native english speaker and from my own background, but I do believe the same applies directly in the english terms. In weapon lingo direct impingment means that the gas is lead to the action of the weapon where it will cause the movement of the action. It doesn't matter what kind of part starts the mechanical motion in the action. Wikipedia says it like this:
Direct impingement is a type of gas operation for a firearm that directs gas from a fired cartridge directly to the bolt carrier or slide assembly to cycle the action.
And continues like so:
The premier current example of direct impingement is the AR-15/M16 rifle designed by Eugene Stoner who first designed the Armalite AR-10. In the Stoner system covered by U.S. Patent 2,951,424, gas is routed from a port in the barrel directly to a chamber formed in the bolt carrier. The bolt acts as the piston and is sealed with small automobile-style piston rings.
Regardless the fact that the Bolt acts as a piston the operating system is called direct gas impingment because the piston is located within the BCG.
Words exist to communicate information. There is a profound difference in the way M4 and HK416 function that leads to differences in their operation and maintenance. To communicate those many subtle differences between those two rifles function and operation one of the rifles is called "direct gas impingment" operated and another one "short-stroke piston operated". By using those couple of words a person who knows weapons can very easily tell the difference between the two to another person of the same caliber.
You can say DI AR-15 has a piston. You can say even that it is piston operated. (Who's going to stop you?) But if you do, you are not communicating very clearly because of the meaning the words have to other people. You are making noise instead of signal, if you will, and confusing a matter that is clear if we take the words in their original meaning.
sinlessorrow
11-03-12, 12:27
In the very same way you could say the Ljungman DI system uses a piston. It does (the carrier that moves because of the gas pressure).
I can come up with exactly two ways (not saying there aren't other...) of converting pressure in to mechanical action: piston and turbine.
What you are arguing is semantics, not mechanics. I speak as a non native english speaker and from my own background, but I do believe the same applies directly in the english terms. In weapon lingo direct impingment means that the gas is lead to the action of the weapon where it will cause the movement of the action. It doesn't matter what kind of part starts the mechanical motion in the action. Wikipedia says it like this:
And continues like so:
Regardless the fact that the Bolt acts as a piston the operating system is called direct gas impingment because the piston is located within the BCG.
Words exist to communicate information. There is a profound difference in the way M4 and HK416 function that leads to differences in their operation and maintenance. To communicate those many subtle differences between those two rifles function and operation one of the rifles is called "direct gas impingment" operated and another one "short-stroke piston operated". By using those couple of words a person who knows weapons can very easily tell the difference between the two to another person of the same caliber.
You can say DI AR-15 has a piston. You can say even that it is piston operated. (Who's going to stop you?) But if you do, you are not communicating very clearly because of the meaning the words have to other people. You are making noise instead of signal, if you will, and confusing a matter that is clear if we take the words in their original meaning.
Well according to the inventor the AR-15 is not a DI system. The the original meaning was at some point changed to DI by whoever made it up.
Also using wikipedia as a source is laughable, there is a reason they are not allowed for college papers. Its worth noting that crapapedia also states that the excess heat from the "DI system" affect the temper of the metals thus reducing parts life......yeah those extra 40*F will surely do that....hope you never go from a hot to cold environment if you do the temper of the metal will be altered.....
That is why no one seriously allows wikipedia as a source.
Well according to the inventor the AR-15 is not a DI system. The the original meaning was at some point changed to DI by whoever made it up.
Also using wikipedia as a source is laughable, there is a reason they are not allowed for college papers. Its worth noting that crapapedia also states that the excess heat from the "DI system" affect the temper of the metals thus reducing parts life......yeah those extra 40*F will surely do that....hope you never go from a hot to cold environment if you do the temper of the metal will be altered.....
That is why no one seriously allows wikipedia as a source.
Now you are just simply being silly.
Well according to the inventor the AR-15 is not a DI system. The the original meaning was at some point changed to DI by whoever made it up.
Also using wikipedia as a source is laughable, there is a reason they are not allowed for college papers.
What is the definition of direct impingment? I could not find it anywhere else.
Also, DI by definition has a piston. It seems the only difference is the location (in the reciever = DI?) Gas is compressed and puts pressure on a surface inside of another surface causing it to move. My buddy's mas acts like this.
sinlessorrow
11-03-12, 12:49
Now you are just simply being silly.
How am I being silly? I could browse wikipedia and point out 100+ topics with incorrect information. I have also never seen a college allow wikipedia as a source either.
As I pointed out it states that the heat from the DI system will affect the temper of the BCG parts, this is false and the heat of Stoners design is generally at most 40*F more than that of the short stroke piston. 40*F will not affect the temper of the steel.
What is the definition of direct impingment? I could not find it anywhere else.
Also, DI by definition has a piston. It seems the only difference is the location (in the reciever = DI?) Gas is compressed and puts pressure on a surface inside of another surface causing it to move. My buddy's mas acts like this.
The Mas-49 a ljungmann are DI guns, with those the gas travel down a tube and strikes the outside of the carrier and forces it back.
The Stoner system send the gas into an expansion chamber where it expands pushing against the piston of the bolt which as it expands causes the carrier to move rearward, unlocking the bolt and venting excess gas. The stoner system is incredibly different from the former 2 DI rifles and has more in common with a piston system, this is just internal.
How am I being silly? I could browse wikipedia and point out 100+ topics with incorrect information. I have also never seen a college allow wikipedia as a source either.
I managed to learn that definition quite a few years before the Wikipedia was born. I do not care if that is a good source for college or not, as long as I know the information in my source is correct. I managed to get my masters without online sources all together so I do not quite know what is hip and what not in the digital age.
And E. S. didn't invent DI operating system so I don't really care what he calls it either. In his system gas is used directly to push the bolt carrier open and in my books that is as DI as it gets. It isn't really clear to me why he opted to use the bolt as a counterpiece instead of a simple MAS-49 like system, but again, that doesn't change the fact: gas is led to the carrier to operate the system.
The stoner system is incredibly different from the former 2 DI rifles and has more in common with a piston system, this is just internal.
Well it is incredibly more complicated and prone to malfunction, that much is for sure.
And no it is not a piston operating system. Not even if you keep repeating it over and over again.
(Why on earth do you have an obsession to call it one anyway? It doesn't change what it is. )
sinlessorrow
11-03-12, 13:11
Well it is incredibly more complicated and prone to malfunction, that much is for sure.
And no it is not a piston operating system. Not even if you keep repeating it over and over again.
(Why on earth do you have an obsession to call it one anyway? It doesn't change what it is. )
Prone to malfunction huh? Guess my rifles and those of almost everyone here never got the memo that they just shouldnt run. Better go tell filthy 14 it is prone to malfunction so it clearly can't have gone 34,000 rounds without failing.
sinlessorrow
11-03-12, 13:12
Mas-49
http://www.sturmgewehr.com/bhinton/MAS49_Manual1950/MAS_49Diagram1950Large.jpg
Ljungman
http://www.gotavapen.se/gota/artiklar/ag42/gaskanal_rtn900w.jpg
In both instances the gas acts directly on the outside of the carrier, striking it and forcing it to recoil.
Now look at the stoner system. It uses an internal piston design to cycle the action.
http://img593.imageshack.us/img593/9981/jody6.jpg
I obviously know all this, so what is your point exactly?
Prone to malfunction huh? Guess my rifles and those of almost everyone here never got the memo that they just shouldnt run. Better go tell filthy 14 it is prone to malfunction so it clearly can't have gone 34,000 rounds without failing.
You are being silly again. Are you seriously claiming that AR15 DI system is not more complex and prone to malfunction than MAS-49? For example MAS system has no sealing rings and no carrier key that can fail. Nor does it lead carbon debris between the bolt and the carrier.
sinlessorrow
11-03-12, 13:28
You are being silly again. Are you seriously claiming that AR15 DI system is not more complex and prone to malfunction than MAS-49? For example MAS system has no sealing rings and no carrier key that can fail. Nor does it lead carbon debris between the bolt and the carrier.
Is it more complex? Sure it is, so is every other semi auto carbine out there today.
You said the Stoner system is prone to failure, I'm saying its not.
You said the Stoner system is prone to failure, I'm saying its not.
I'm saying more than the MAS one. More "complicated and prone to failure" to be exact.
(MAS was in Vietnam ten years before the AR-15 and it just didn't care what kind of powder it was fed. Or have you heard about them failing in combat? So, in that light I think I made a reasonable statement about it being more reliable.)
Isn't A di system a type of piston? As in the picture of the mas, there is t tube inside of a tube. As I understand it dis have pistons unless the gas hits a flat surface. It all seems to be semantics where di denotes a specific type of piston. If not, what is the differences as I'm interested in these things?
sinlessorrow
11-03-12, 17:49
Isn't A di system a type of piston? As in the picture of the mas, there is t tube inside of a tube. As I understand it dis have pistons unless the gas hits a flat surface. It all seems to be semantics where di denotes a specific type of piston. If not, what is the differences as I'm interested in these things?
The difference is the Mas and ljungmen do not have an expansion chamber that contains a piston with gas rings.
The mas and ljungmen go down a tube that is shrouded bythe bolt carrier, at this point they hit the bolt carrier and cycle it that way.
In the AR-15 the gas goes into an expansion chamber and expand against the bolt tail that has gas rings to create a seal. The bolt tail is basically a piston.
The expansion chamber and the bol tail perform the same function as say the piston and expansion chamber on a piston AR-15. Gas enters the chamber, expands opening the piston which forces the op rod to strike the BCG to cycle it then expells the gas.
In the stoner system you basically move that chamber into the BCG and get rid of the op rod. Gas enters the chamber, expands opening the piston(bolt in this case as the carrier moves rearward) then expells excess gas.
Let's keep the tone civil please, and let's leave the "build" "assemble" argument out of this. It has nothing to do with how an AR gas system works.
A piston does not need rings to make it a piston.
...So what you are trying to tell me is that when Eugene Stoner, the designer of the gas system in this discussion wrote in the patent that this isn't a direct impingement system, he was wrong?...
Only in the same way that Edison was wrong if he ever said his incandescent bulb was not a torch.
This argument does not work for me. A torch is a complete device that gives off light, it's source being flame (per the usual definition) or by an electric bulb (the English call a flashlight an "electric torch").
Edison's incandescent bulb is only a part of a lighting device like the gas system is only a part of a complete rifle.
He can call it anything he wants. It still does not diminish the fact that a redirected expanding gas impinges, imparts, strikes with a force on the surfaces of a closed system until something gives way.
The gas system isn't closed anymore than a gas block piston system is.
Actually, reducing the discussion down to "is/is not a DI" has nothing to do with how the system works and is a side track.
Perhaps the AR gas system does fit the definition of direct impingement. Perhaps the teat on the carrier of the Ljungman is a piston. In the simplest terms, it performs the same function.
In the simplest terms, the gas directly impinges on the piston of a piston & op-rod system. To differentiate between the two systems, you'd have to call one a carrier driven direct impingement system and the other a piston driven direct impingement system.
However, the piston of the AR and Ljungman complicates that definition. In the case of the Ljungman, the piston is part of the carrier, so we can justify calling it a carrier driven direct impingement system.
But the piston of the AR isn't part of the carrier (although it's part of the bolt carrier group). It reciprocates inside the carrier as the carrier reciprocates inside the upper. It should be called a "carrier driven, reciprocating piston direct impingement system".
See where this is going? Lots of talking in circles. My conclusion is the AR does indeed have a piston & cylinder and that the gases directly impinge on something, whether it's the carrier or the piston. In the AR, the gases impinge on both
This argument does not work for me.
I meant that both the torch and the light bulb produce light by burning a fuel of some sort, wood etc. for the torch, and carbon for the light bulb. Stoner can make the claim that his system is not a traditional DI system only when viewed extremely closely. Stoner's design is a measurable improvement when compared with a traditional DI systems and piston systems, so it qualifies under our system for patents. That does not mean that his system is so different that it does not fit the basic description of a DI system, just the same as Edison's bulb fits the basic description of a torch. Stoner's design IS a DI system, just not the only one.
In the AR, the gases impinge on both
But it is the carrier, not the bolt, that is actuated by the gas. In all the DI systems the gas does two things, one is push the bullet down the barrel, and the other is reciprocate the carrier. In a piston system the gas moves the bullet, and a piston that strikes the carrier in many cases.
But it is the carrier, not the bolt, that is actuated by the gas. In all the DI systems the gas does two things, one is push the bullet down the barrel, and the other is reciprocate the carrier. In a piston system the gas moves the bullet, and a piston that strikes the carrier in many cases.
This.
And the location where the force of the gas is transformed into mechanical motion. In long- and short stroke piston designs pressure is turned into mechanical force at the gas port. In direct impingment pressure itself is turned into mechanical motion at the BCG and the energy to do so is conveyed as gas pressure from the gas port instead of a solid connection.
But the piston of the AR isn't part of the carrier (although it's part of the bolt carrier group). It reciprocates inside the carrier as the carrier reciprocates inside the upper. It should be called a "carrier driven, reciprocating piston direct impingement system".
The bolt does NOT reciprocate, as in the sense of a reciprocating mass. The bolt is pulled out of battery, then pushed back into battery by the bolt carrier because of the cam pin. Remove the cam pin and the bolt will stay put, and the bolt carrier will still reciprocate when the round is fired (Don't do this!). The bolt's movement is due to the reciprocating motion of the bolt carrier.
The bolt does NOT reciprocate, as in the sense of a reciprocating mass. The bolt is pulled out of battery, then pushed back into battery by the bolt carrier because of the cam pin. Remove the cam pin and the bolt will stay put, and the bolt carrier will still reciprocate when the round is fired (Don't do this!). The bolt's movement is due to the reciprocating motion of the bolt carrier.
Removing the cam pin will result in the bolt being left in the barrel extension, but removing a piston rod inside an engine will have the same result.
Sure, the bolt's movement is due to the motion of the carrier, but the fact is, the bolt does move in relationship to the carrier. It's all relative as explained by Albert Einstein. It is also correct to say the AR piston of the AR pushes the rifle forward in relationship to the cylinder (carrier) because if the cylinder were fixed in place, that's what would happen. If this were impossible, "limp wristing" a self loading pistol would be impossible. Limp wristing occurs because the frame moves rearward in relationship to the slide enough that the slide cannot move rearward enough in relationship to the frame to fully function. It's understanding these principles that an engineer can make things work and make them work more efficiently.
It doesn't matter how you slice it, the bolt is a piston and the carrier is a cylinder. They convert the energy of the expanding gases into mechanical motion
Suwannee Tim
11-04-12, 09:04
The bolt does NOT reciprocate.......
The bolt does reciprocate. Decades ago, as a graduate student in mechanical engineering I taught Kinematics and Dynamics of Machine Elements to juniors. A couple of things I taught them: 1) words mean things and 2) reciprocate means to move in and out, up and down, back and forth, generally on a rectilinear path. It's a lot easier to get definitions now that it was back then. Then you had to look them up in a dictionary. Now you just type them in a search box:
Let me Google that for you. (http://lmgtfy.com/?q=reciprocate)
The bolt does reciprocate.
It no more reciprocates than the connecting rod in an engine. The connecting rod has more than two displacements in it's motion. One end of the connecting rod moves in a reciprocating motion, the other end moves in a circular motion, while the arm moves both laterally and longitudinally.
The bolt moves both longitudinally and rotates (though for a very short distance) along the line of travel, and only moves due to the bolt carrier pulling it out of battery.
In the strictest sense, if a cylinder moves instead of the piston, the piston is stationary. The fact that the bolt is moved to cause another action to occur is the genius of this system.
It no more reciprocates than the connecting rod in an engine. The connecting rod has more than two displacements in it's motion. One end of the connecting rod moves in a reciprocating motion, the other end moves in a circular motion, while the arm moves both laterally and longitudinally.
The bolt moves both longitudinally and rotates (though for a very short distance) along the line of travel, and only moves due to the bolt carrier pulling it out of battery.
In the strictest sense, if a cylinder moves instead of the piston, the piston is stationary. The fact that the bolt is moved to cause another action to occur is the genius of this system.
Eugene Stoner refers to only PART of the bolt as a Piston. This is the part with groove/rings that seal the gas within the expanding gas cylinder.
I suppose we can argue semantics all day long, but the inventor's patent calls this particular part of said item "a piston".
Now, I have yet to see a corpse rise up and declare to the MD "It wasn't cardiac death you dolt, it was a PE". What I mean is...why are we arguing over terms used to describe a system that we fully understand the function of? The "correct" understanding of such terms will lead to absolutely no better performance of that which they describe.
It no more reciprocates than the connecting rod in an engine. The connecting rod has more than two displacements in it's motion. One end of the connecting rod moves in a reciprocating motion, the other end moves in a circular motion, while the arm moves both laterally and longitudinally.
The bolt moves both longitudinally and rotates (though for a very short distance) along the line of travel, and only moves due to the bolt carrier pulling it out of battery.
In the strictest sense, if a cylinder moves instead of the piston, the piston is stationary. The fact that the bolt is moved to cause another action to occur is the genius of this system.
You need to do more research and studying on the subject
You need to do more research and studying on the subject
What in dynamic mechanics. No one has even mention the fact that the bolt displays a rotary reciprocation, until now (unless I missed in the previous 11 pages).
We know the bolt rotates. That's how it locks and unlocks. But the rotation does not mean the back and forth motion is not reciprocation
-or did I misunderstand your post?
The difference is the Mas and ljungmen do not have an expansion chamber that contains a piston with gas rings.
The mas and ljungmen go down a tube that is shrouded bythe bolt carrier, at this point they hit the bolt carrier and cycle it that way.
In the AR-15 the gas goes into an expansion chamber and expand against the bolt tail that has gas rings to create a seal. The bolt tail is basically a piston.
Okay, so since the true DIs gas expands directly from the gas tube its "DI" while the AR has a separate chamber for expansion. Even though its a continuous flow, its different. Like pipes going to a tank, its one solid flow of fluid, but a tank is not a pipe. Is this a relatively decent analogy because I think I'm starting to get this.
The expansion chamber and the bol tail perform the same function as say the piston and expansion chamber on a piston AR-15. Gas enters the chamber, expands opening the piston which forces the op rod to strike the BCG to cycle it then expells the gas.
In the stoner system you basically move that chamber into the BCG and get rid of the op rod. Gas enters the chamber, expands opening the piston(bolt in this case as the carrier moves rearward) then expells excess gas.
Ok, thank you for the explanation... so do you all think maybe its technically a hybrid system since there is no oprod? Or am I still a little ignorant of the semantics?:)
Removing the cam pin will result in the bolt being left in the barrel extension, but removing a piston rod inside an engine will have the same result.
Actually, I'm fairly certain that if you removed the rod the piston would be unable perform its function of harnessing the combusted energy and converting it to motion. The result would simply be the piston being blown out the end of the cylinder. The "Piston" in the AR is different as if you were to disconnect it from the carrier the gun could still fire at least once and the carrier would still cycle. The presence of a "Piston" on the bolt of the AR is not integral to the function of the mechanical parts, therefore it is not and should not be referred to as a Piston weapon IMHO.
sinlessorrow
11-04-12, 19:31
Actually, I'm fairly certain that if you removed the rod the piston would be unable perform its function of harnessing the combusted energy and converting it to motion. The result would simply be the piston being blown out the end of the cylinder. The "Piston" in the AR is different as if you were to disconnect it from the carrier the gun could still fire at least once and the carrier would still cycle. The presence of a "Piston" on the bolt of the AR is not integral to the function of the mechanical parts, therefore it is not and should not be referred to as a Piston weapon IMHO.
The piston on the end of the bolt is very integral to the function of the mechanical parts.
If it was not there the rifle would not function. You can also say that if the barrel and cam pin was not there the bolt would be blown out of the cylinder.
The piston on the end of the bolt is very integral to the function of the mechanical parts.
The Piston being there is integral, but not the fact that it is connected to the carrier. As with the example I was referring to in a "Piston AR" if you remove the Rod the piston will not move the carrier when the gas hits it. In the Stoner AR if you disconnect the bolt the carrier will still move. That IS a definable difference between the two designs, therefore we can safely say that one is not the other. The same can not be said of the other DI designs and Stoner's AR.
Suwannee Tim
11-04-12, 20:11
It no more reciprocates than the connecting rod in an engine........
Whatever you say Gun. Whatever you say.
sinlessorrow
11-04-12, 22:16
The Piston being there is integral, but not the fact that it is connected to the carrier. As with the example I was referring to in a "Piston AR" if you remove the Rod the piston will not move the carrier when the gas hits it. In the Stoner AR if you disconnect the bolt the carrier will still move. That IS a definable difference between the two designs, therefore we can safely say that one is not the other. The same can not be said of the other DI designs and Stoner's AR.
Actually you said
The presence of a "Piston" on the bolt of the AR is not integral to the function of the mechanical parts, therefore it is not and should not be referred to as a Piston weapon IMHO.
So yes the piston is ingetral to the function of the mechanical parts, which is opposite of wht you said in the quoted text.
Also you cannot simply disconnect the piston since it is attached to the bolt, but if you machined it off and disconnected it that way, then no the carrier would do nothing.
Also you cannot simply disconnect the piston since it is attached to the bolt
I was referring to disconnecting it from the carrier, not the bolt. The point was to illustrate the difference in the two systems. If you disconnect the Piston in a Piston System, and the bolt in Stoner's AR, one will cycle the carrier and one will not, therefore they are not the same.
I apologize if I am not being clear enough, I'm still learning about this stuff. Splitting hairs just happens to be another one of my hobbies :fie:
sinlessorrow
11-04-12, 23:23
I was referring to disconnecting it from the carrier, not the bolt. The point was to illustrate the difference in the two systems. If you disconnect the Piston in a Piston System, and the bolt in Stoner's AR, one will cycle the carrier and one will not, therefore they are not the same.
I apologize if I am not being clear enough, I'm still learning about this stuff. Splitting hairs just happens to be another one of my hobbies :fie:
If you disconnected the piston in the AK it would still cycle the bolt.
You see where I am going with this?
If you disconnected the piston in the AK it would still cycle the bolt.
How do you figure? If you were to remove the rod as with the example I was referring to you would just end up with the piston traveling down the cylinder and hitting the carrier. Sure it might move the carrier, perhaps enough even to allow gas to escape past, but not to the same extent that it would have moved it with the rod in place. With the rod removed the amount of energy transferred to the carrier is diminished, and thus the carrier wouldn't cycle under otherwise normal circumstances.
How do you figure? If you were to remove the rod as with the example I was referring to you would just end up with the piston traveling down the cylinder and hitting the carrier. Sure it might move the carrier, perhaps enough even to allow gas to escape past, but not to the same extent that it would have moved it with the rod in place. With the rod removed the amount of energy transferred to the carrier is diminished, and thus the carrier wouldn't cycle under otherwise normal circumstances.
AR and AK both, if you remove the piston rod(or any part of the piston system), they will not cycle. If you disconect it, they will (at least back, the ak might bind up on the way foreward) at least some of the time. Also, the cam pin has to do with the lockup, not the gas system. It has no part in it. Cam-pin removed you still have a piston.
Also, the cam pin has to do with the lockup,
The cam pin holds the bolt and supposed piston to the carrier, and thus would be the equivalent of the rod in a Piston system.
If the pin is removed the AR will still cycle as the expansion chamber is not compromised and the same amount of energy is transferred to the carrier. The bolt would simply stay locked up and the carrier would travel rearward and forward. (ideally)
If we are to go by the traditional definition of "piston", then it is the carrier that would be the piston as it is the part of the system that converts the gas energy to movement which is then stored in the spring. The bolt only moves because it is attached to the carrier, and only AFTER the carrier has absorbed enough energy to complete its cycle if I understand the process correctly. From where I stand it seems that the AR BCG is the reverse of a traditional piston system. Should we still call it a Piston if that is the case?
Failure2Stop
11-05-12, 06:02
When research on firearms leads one to argue semantics about naming conventions, one should really ask one's self, "self, would John Wayne and Clint Eastwood be having this argument?"
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