PDA

View Full Version : Gas piston question



ChromeLined
08-02-06, 01:02
So what do you guys think is the closest piston system for the AR available to us thats like or operates like the H&K 416 system?

K.L. Davis
08-02-06, 01:05
The HK does nothing more than push back on a modified bolt key with an oprod, just like any of the half dozen other systems out there... where they are unique is in how the piston is regulated and the gas vented -- it is the G36 design and protected by patent.

Steel_Weasel
08-02-06, 10:41
So what do you guys think is the closest piston system for the AR available to us thats like or operates like the H&K 416 system?

The closest one is from a company that many people wouldn't buy from right now.

K.L. Davis
08-02-06, 13:28
The closest one is from a company that many people wouldn't buy from right now.

Actually the LW entry does not use a true piston per se... it uses a "cup and spigot" design made popular years ago by rifles such as the AR18/180 -- it is simple design and regulates itself well.

POF uses a cartridge piston design... naturally there were some early growing pains and learning, but Frank has stayed true to continued improvment and has a really nice system.

The HK system has the piston set rather high above the bore axis... this is the reason behind some of modifications that are peculiar to the design.

All of the systems suffer the same problems -- back about 20 years ago the systems would shear bolt keys with frightening predictability, today's systems have beefed up and modified keys... now we are seeing that "bolt tilt" is becoming a concern.

The concept is still in genisus... whereas in the past, designers simply gave up when presented with problems, people today are putting some clever thought into overcoming these issues. I would speculate to say that the future will see a design that is not a retrofit to the existing platform and bares little resemblance to what is out there now.

ChromeLined
08-03-06, 22:41
Thanks guys..im gonna give the POF a shot:D

Nitrox
08-03-06, 23:19
.....

VA_Dinger
08-03-06, 23:30
Thanks guys..im gonna give the POF a shot:D

Good decision

JLM
08-04-06, 01:38
KL, can you talk about the Colt guns just for comparison purposes?

mtdawg169
08-04-06, 08:31
I have heard about concerns over bolt tilt also. What is it & what concerns does it create exactly?

TigerStripe
08-05-06, 20:17
I have heard about concerns over bolt tilt also. What is it & what concerns does it create exactly?

I'd like to know that too. For now, I'd go with a POF or Colt.

TS

Steel_Weasel
08-07-06, 11:57
I have heard about concerns over bolt tilt also. What is it & what concerns does it create exactly?

Let me preface this by saying that I'm not an engineer and don't know alot of the technical terms related to 'bolt tilt' so I will try and describe it, as much as I know, in laymans terms.

In DI, the gas enters the bolt carrier key inline with the direction of bolt movement. With piston systems (416, LW, ?) the momentum imparted to the 'piston' strikes the bolt carrier 'head' (there is no longer a traditional key) is transferred at an angle. From what I know, this is mostly because the front gas port is lower than the entry port in the upper receiver resulting in the back of the bolt carrier tilting downward when the piston strikes the bolt carrier head.

Bolt tilt is mitigated/eliminated in the before mention systems by the use of a special bolt carrier with a slightly larger profile at the rear to phyiscally prevent the bolt from tipping.

I don't know if the POF system has bolt tilt issues as it's bolts do not have this 'thickened' rear. I'm speculating that POF doesn't have bolt tilt because it's front gas port is higher and allows the piston to impart momentum along the same axis as a DI system.

Did I get it right ?

K.L. Davis
08-07-06, 12:34
Let me preface this by saying that I'm not an engineer and don't know alot of the technical terms related to 'bolt tilt' so I will try and describe it, as much as I know, in laymans terms.

In DI, the gas enters the bolt carrier key inline with the direction of bolt movement. With piston systems (416, LW, ?) the momentum imparted to the 'piston' strikes the bolt carrier 'head' (there is no longer a traditional key) is transferred at an angle. From what I know, this is mostly because the front gas port is lower than the entry port in the upper receiver resulting in the back of the bolt carrier tilting downward when the piston strikes the bolt carrier head.

Bolt tilt is mitigated/eliminated in the before mention systems by the use of a special bolt carrier with a slightly larger profile at the rear to phyiscally prevent the bolt from tipping.

I don't know if the POF system has bolt tilt issues as it's bolts do not have this 'thickened' rear. I'm speculating that POF doesn't have bolt tilt because it's front gas port is higher and allows the piston to impart momentum along the same axis as a DI system.

Did I get it right ?

Pretty close... I have to say that I am not avoiding this topic, but a lot of the research and design work done by a manufacturer to eliminate the problem needs to be treated as trade secret for now -- But I can say that a lot of work is being done to eliminate the problem. Guess what I am is saying is that there are potential answers out there, but they have come at the investment of the time and money of a couple of good people... so let's let them do with that info what they will.

Couple of things: It does not matter where the front of the oprod is, the length of the arm at the bolt is the same for all the designs (actually, one company is a little longer) -- no design that uses a modified AR bolt carrier is exempt from the problem.

Certain type of "pistons" are worse than others, as some designs push in a rather steady, slow way... while others push with a sudden, snappy force.

Redesigned bolts do not prevent the problem, they simply take a little onger to wear down...

mtdawg169
08-07-06, 13:22
Pretty close... I have to say that I am not avoiding this topic, but a lot of the research and design work done by a manufacturer to eliminate the problem needs to be treated as trade secret for now -- But I can say that a lot of work is being done to eliminate the problem. Guess what I am is saying is that there are potential answers out there, but they have come at the investment of the time and money of a couple of good people... so let's let them do with that info what they will.

Couple of things: It does not matter where the front of the oprod is, the length of the arm at the bolt is the same for all the designs (actually, one company is a little longer) -- no design that uses a modified AR bolt carrier is exempt from the problem.

Certain type of "pistons" are worse than others, as some designs push in a rather steady, slow way... while others push with a sudden, snappy force.

Redesigned bolts do not prevent the problem, they simply take a little onger to wear down...

OK, so other than obvious potential problems with wear on the upper receiver & bolt carrier, what are the other "side effects" of bolt tilt? Is it a wear issue or does it affect extraction, reliability, etc.?

l2e
08-07-06, 14:56
Not to turn this into this system is better than that system, but I have a shorty POF gas piston upper and have around 3k-5k rounds through it (Wolf mainly) and have yet to clean it. It still runs perfect. I have a buddy who just got a LW and if their QC is any indication of their piston design, then they can keep their rifle. The rifle came with surface rust all over the rifle...not acceptable. I have bought and sold many a rifle and never seen that bad of QC or lack thereof.

SuicideHz
08-07-06, 15:23
Not to turn this into this system is better than that system, but I have a shorty POF gas piston upper and have around 3k-5k rounds through it (Wolf mainly) and have yet to clean it. It still runs perfect. I have a buddy who just got a LW and if their QC is any indication of their piston design, then they can keep their rifle. The rifle came with surface rust all over the rifle...not acceptable. I have bought and sold many a rifle and never seen that bad of QC or lack thereof.

You definitely made the better choice. ;)

ChromeLined
08-07-06, 21:56
Surface rust evevn on the upper and lower? god where was it kept before shipping.:eek:

l2e
08-08-06, 12:06
Just off the top of my head, there was an enormous amount of surface rust on the bolt catch and ejection door. Then there was some minor on the FSB. Just unacceptable.

variablebinary
08-08-06, 13:12
So what do you guys think is the closest piston system for the AR available to us thats like or operates like the H&K 416 system?

In terms of operation I cant say which is more like the HK, but I do like the POF system. For the price they give you the world in terms of features.

Also POF is as close as we have to a piston standard currently, with both Bushmaster and DSA choosing them which should make for easier parts buying and competition.

On top of that the POF guys are top notch and of good character as far as I can see.

ChromeLined
08-09-06, 21:26
Thanks Variablebinary...im a norotic like that..with Bushy and DSA using it that makes it kind of the standard in piston systems.What does POF charge for an upper and can they do it on any barrel legnth.I emaile Bushy and they said they only do it on a 16" M4 profile..I want a 14.5/phantom HBAR A2 upper and can it be done with a standard FSB in place?...thanks...Dave

variablebinary
08-10-06, 00:30
Thanks Variablebinary...im a norotic like that..with Bushy and DSA using it that makes it kind of the standard in piston systems.What does POF charge for an upper and can they do it on any barrel legnth.I emaile Bushy and they said they only do it on a 16" M4 profile..I want a 14.5/phantom HBAR A2 upper and can it be done with a standard FSB in place?...thanks...Dave

Contact POF. They seem to build almost any config. AFAIK they have a 14.5" version here is a small pic

http://www.pof-usa.com/P-416/photos/DSC0192244.JPG

Sean King
08-10-06, 19:41
Pretty close... I have to say that I am not avoiding this topic, but a lot of the research and design work done by a manufacturer to eliminate the problem needs to be treated as trade secret for now -- But I can say that a lot of work is being done to eliminate the problem. Guess what I am is saying is that there are potential answers out there, but they have come at the investment of the time and money of a couple of good people... so let's let them do with that info what they will.



Can you say what manufacturer? Sorry, new to the board and don't know who's who or even which industry partner you work for.

I wish I could still access my IM's from Arf.com, as I could at least post PLW's comment about carrier lift (same thing as carrier "tilt") and how his system adressed it...(more to it that just the boss at the end of the carrier). While I'm sure many of you wouldn't believe him about this issue after his past deeds, I'd be interested in hearing your educated comments as I bought his explanation hook, line and sinker. In fact, that explanation was the main reason I went with the LW over the POF.

As for POF....they address carrier lift by making the barrel nut physically longer, which guides the op rod for a longer duration and makes the carrier itself larger so that there's less slop between it and the receiver......at least that's the jist (as I understood it) from Frank when I asked him the same questions I asked Paul. I don't know if Frank is a member here.....if so, perhaps he will be along to give a better explanation than a moron like me could ever hope to. :)

I can definitely vouch for Frank at POF for being a great guy. I'd would have owned a POF rifle by now if I hadn't been bamboozled by Paul/HFG/CmdrColt/etc.

Frank's rifles offer a lot for the money.....heavy profile, fluted Mike Rock bbls, the nickle silica (I think?) coated carrier and piston parts, free float rails, etc. for right around a thousand . I know a lot of people don't care for his Predator rails, but that is one thing I really like about it (I'll admit mainly for looks, but also for the heat dissipation). It is a little on the big side (which is okay since I have fat hands), but is a strong, free float design, IMO. The only thing I mildly dislike about POF's rifle versus the LW (once I'd seen both in person) is that the POF seems noticeably heavier and the piston system didn't *seem* as refined; not that it isn't.....just in my admittedly uneducated opinion it isn't.

As for service......Frank has been great. He has always seemed very approachable and knowledgeable about his product, has been completely honest to pointed questions and is really willing to work with the customer if you want something custom.

Someone asked a question about custom barrel lengths with the POF. I know they offer a 9.25", 11.5", 14.5", 16", and 18". He even tried some experimental 13.6" bbls (sorta at my suggestion) with Krink FHs.....unfortunately, the dissipator look I was going for wouldn't work with that set up b/c the gas plug couldn't be removed without removing the Krink and that was to be permenantly attached to avoid having to register as an SBR. They are also working on .308, 6.5 Grendel and maybe even a 6.8 SPC by the end of year.

From what I've heard from Frank, his system, not LW's is the most like HK's.

HTH,
Sean

ChromeLined
08-10-06, 22:00
Thanks guys im gonna go POF..thanks avriablebinary and sean.Im glad it can be had in 14.5..they do use chrome lined barrels I assume.

variablebinary
08-10-06, 23:05
Thanks guys im gonna go POF..thanks avriablebinary and sean.Im glad it can be had in 14.5..they do use chrome lined barrels I assume.

Barrels are chrome lined, as are all the piston parts, the bolt carrier group, and the inside of the upper is nickle plated for "lubless" operation
POF goes way beyond every other piston maker to ensure fouling doesnt hamper weapon performance.

ChromeLined
08-10-06, 23:19
How does nickle perform say in wet rainy environments?is it resistant to corrosion to?..thanks man..Dave

K.L. Davis
08-10-06, 23:23
Can you say what manufacturer? Sorry, new to the board and don't know who's who or even which industry partner you work for.

Sean

Sorry... just keep posted here though for new stuff now and then.

I don't work for any manufacturer -- they all want to pay me what I am worth and I just won't work that friggin cheap!

K.L. Davis
08-10-06, 23:24
How does nickle perform say in wet rainy environments?is it resistant to corrosion to?..thanks man..Dave

NP is not great for corrosion resistance... it is better than untreated steel of course, but it holds lubricants very well.

Sean King
08-11-06, 07:18
Sorry... just keep posted here though for new stuff now and then.

I don't work for any manufacturer -- they all want to pay me what I am worth and I just won't work that friggin cheap!
:) :D

Thanks for the reply. I'll stay tuned then. ;)

Sean

PS. sorry about the nickle silicon coating flub.....VB is right....all the piston parts and carrier are hard chromed (not exactly sure which chrome....but corrosion resistant). The inside of the receiver is what's nickle coated. Hope that clears up my miswording.

ChromeLined
08-11-06, 22:25
To KL Davis..do think then its not good for the inside of the POF upper to be nickle plated.

K.L. Davis
08-11-06, 22:38
To KL Davis..do think then its not good for the inside of the POF upper to be nickle plated.

I think Frank is using NiB or something like that... Nye-Carb would be the best plating that I can think of, it is a nickel and silicone carbide plating.

The upper is not subject to corrosion, a plating like NiB or Nye-Carb is the best choice...

ChromeLined
08-12-06, 01:15
Excellent..thanks KL...Dave:D

Sean King
09-05-06, 22:58
Sorry to bring back the dead, but I found this quote from the LWRC camp about carrier lift and was curious as to twl's and Mr. Davis' take on it.

"The system is more than a piston cup, nozzle and spring. The LW system has a completely proprietary bolt carrier and key. The key ever so slightly sloping to vector the forces on the carrier in a manner that carrier tilt is eliminated. The addition of a boss base on the back of the bolt carrier also to prevent the possibility of bolt bounce related to carrier tilt. It ELIMINATES all possibility of carrier tilt.


Have either of you examined LW's system to corroborate or deny the claim? Eliminating carrier lift would be of obvious benefit to a gas piston system working in an AR platform. Just curious as to your opinions.

Thanks,
Sean

twl
09-06-06, 10:16
Sorry to bring back the dead, but I found this quote from the LWRC camp about carrier lift and was curious as to twl's and Mr. Davis' take on it.

"The system is more than a piston cup, nozzle and spring. The LW system has a completely proprietary bolt carrier and key. The key ever so slightly sloping to vector the forces on the carrier in a manner that carrier tilt is eliminated. The addition of a boss base on the back of the bolt carrier also to prevent the possibility of bolt bounce related to carrier tilt. It ELIMINATES all possibility of carrier tilt.


Have either of you examined LW's system to corroborate or deny the claim? Eliminating carrier lift would be of obvious benefit to a gas piston system working in an AR platform. Just curious as to your opinions.

Thanks,
Sean

I have no problems with a carrier change that helps to combat carrier tilt in an overhead piston system.
I haven't done any specific examination of said system to corroborate or deny the claim.
It seems to be something that would work.

SinnFéinM1911
09-06-06, 10:36
Thanks guys..im gonna give the POF a shot:D


Can't go wrong there !

Sean King
09-06-06, 14:04
I have no problems with a carrier change that helps to combat carrier tilt in an overhead piston system.
I haven't done any specific examination of said system to corroborate or deny the claim.
It seems to be something that would work.


Thanks for your comment twl. I really respect your opinion and appreciate your input/advice.

Thanks again,
Sean

AR-180
12-08-06, 13:11
I have an LW. It works reliably and shoots great. I have shot a buddy's LW as well, and it shoots even better.

K.L. Davis
12-08-06, 23:14
I spent some time at the LWRC booth at SAR, and discussions with them are continuing...

As much as I would love to talk about PLW and his string of crap, discression is the better part of honor -- so I'll simply say that they guys that are now LWRC are doing their best to move away from the past, we all know that many of the things that were said about the system in the past were BS, but the guys there now are shooting straight from the hip... errr, sorry... they are doing the right thing :)

9mm MP5 Machinenpistole
12-16-06, 22:11
I have often thought the same, and in my opinion the gas operation system that is the closest to the HK 416 is the Leitner-Wise system. I have recently ordered one and look forward to test firing it!

K.L. Davis
12-16-06, 22:20
I have often thought the same, and in my opinion the gas operation system that is the closest to the HK 416 is the Leitner-Wise system. I have recently ordered one and look forward to test firing it!

Maybe you should have a look at the two of them side by side... the HK uses the G36 piston and LW uses the AR18 cup and spiggot.

VA_Dinger
12-16-06, 22:48
Maybe you should have a look at the two of them side by side... the HK uses the G36 piston and LW uses the AR18 cup and spiggot.

100% correct.

Even though they are both gas piston AR's they do not use the same operating system.

Milkman
12-16-06, 23:15
I spent some time at the LWRC booth at SAR, and discussions with them are continuing...

As much as I would love to talk about PLW and his string of crap, discression is the better part of honor -- so I'll simply say that they guys that are now LWRC are doing their best to move away from the past, we all know that many of the things that were said about the system in the past were BS, but the guys there now are shooting straight from the hip... errr, sorry... they are doing the right thing :)

The PLW shenanigans may be over but there are still a lot of reports of problems (missed delivery promises, poor communication, disorganization, etc).

ABNAK
12-17-06, 08:49
I have a relatively early (circa early 2005) Leitner-Wise converted upper. After 3 weeks became 5 months, excuses flowed, and tempers flared I finally got it. It works fine except for 77gr Mk262 which will fail to extract more often than not (and this is with a D-fender ring in place). In fairness to L-W, they converted a J&T chrome lined upper assembly that I sent them and I feel that the chamber may be a little on the rough side---ER Shaw barrels are what I believe J&T uses and there have been threads about QC issues with them. I feel that with the higher pressure (?) of the Mk262 loads that any otherwise insignificant chamber burrs rear their ugly heads and cause failures to extract. I've had NO problems with M855 or M193. I don't shoot Wolf in any of my AR's.

I also had a POF upper. Well made and reliable. I just didn't like the weight it pushed an M4gery to. I'm no wall-flower but it's heft put it in more of a .308 type category IMHO. I ended up selling it, but I can highly recommend it for a quality gas piston upper.

I also currently have an Ares drop-in system on a Bushy Superlight. Works fine so far and is easy to install. It is about to become a Not-so-superlight as I am going to buy a Midwest Industries rail system and have my buddy mill it out for the piston clearance. According to another board many of you guys frequent a 0.5" ball-end mill will do the trick. I've seen the pics.

So you can see that I had/have all 3 of the currently AVAILABLE (key word there!) piston systems. I like 'em. Clean up is a breeze, which is my personal selling point. I think that they are here to stay, hopefully in a more standardized fashion. However, when people invest the time and money to R&D these things I don't suppose that uniformity will ever happen---unless of course the .mil adopts one.

IIRC the HK416 has a gas piston similar to the M1 Carbine; it is a "tappet" type, right?

As far as carrier bounce is concerned, what kind of signs of wear should one look for? Also, since this is primarily due to the "tap" of the op rod on the carrier, wouldn't a long piece ATTACHED to the carrier (like an AK) preclude this? I realize that it would have to be a long, THIN, strong piece of metal to fit through an AR upper, but with today's metallurgy it surely has to be possible. In other words it would be a bolt carrier with a LONG "key" on it that would slide into a spigot (or whatever) up near the FSB like they already do now. It wouldn't have to have a recoil spring in front of the upper, like the L-W/HK/Ares do, but instead rely on the buffer spring to return everything like the POF does. Just a thought.....

variablebinary
04-14-08, 00:24
And now we have LMT with its QD barrel, multi caliber and most excellent MRP. Lot to like there.

LWRC, POF are very vulnerable to a well done LMT product. One of the key parts of success is market share, and the DI MRP as is has a larger market share than LWRC and POF combined.

LMT has a stronger brand as well

ARin
04-14-08, 01:36
call this thread lazarus, cause you just brought it back from the dead.