View Full Version : So I took various buffers and springs, and a notebook to the range..
...expecting to tune two new ARs. I was really expecting to find a perfect fit for each, which in my mind was a:
~3:00-4.00 ejection with 5.56 and maybe 4:00-4:30 with 223/wolf but function with it.
So I took a 10.5" with .093" (Colt sized) and a 16.5" Middy (Its a Nordic barrel, and they are actually 16.5" to bolt face insead of the 16" advertised) with a .085" gas port. Had standard (on the long side, 11 1/8") and extra power buffer springs (Springco RED), H, Spikes ST-2, H2, and H3 buffers. Both have Denny's BCG build on Young Chrome M16 carriers, which I think have extra power extra springs but blue inserts, no o-ring. Wolf 223, PMC 223, and M193 (Armscor/Philippines). Now I'm complete freaking lost, my results do not make since. I didn't test every configuration, I was frustrated and limited in time. I was expecting both configurations to be overgassed but the Middy more so than the 10.5" carbine.
10.5" 5.56 chamber .093" gas port:
Standard Spring, H Buffer
Wolf 223: 2:30 13ft
PMC: 1:00 5ft
M193: 1:00-1:30 2-5ft
Standard Spring, H3 Buffer
Wolf 223: 3:00 9ft
PMC: 1:30 8ft
M193: 1:30 3-8ft
Heavy Spring, H Buffer
Wolf 223: 2:30 11ft
PMC: 2:00 4-8ft
M193: 2:00 4-8ft
Heavy Spring, H3 Buffer
Wolf 223: 1:30-3:00 5-10ft
PMC: 1:30-2:00 8ft
M193: 1:30-2:00 7ft
Functioned in every setup. The ejection results for the Heavy spring + H3 buffer do not appear to make since. At the time I ordered I follwed the advise to size stuff to colt size so everything would run in it, before I learned this is to much gas. I'm thinking of crushing the gas tube some or buying a adjustable gas block. I'm at a loss, I though a heavy spring and a H3 buffer would tame a colt sized gas port 10.5".
I was running out of time but took out my next rifle:
16" Midlength gas, .085" gas port (per manufactor), 223 wylde chamber:
Standard Spring, Spikes ST-2 (similar to H2)
Wolf: would not feed next rd, appeared to be short stroking
PMC 223: 50/50 results, same
5.56: 4:00 8ft and smooth
Shouldn't .085" gas port with a 16.5" Middy gas system be overgassed? I guess this is perfect if I onlyh shoot 5.56, will try a H next time out. It did function in fa on my selectfire that had a H2 with 5.56. I know another person took a .071" middy and cut it to 12.5" and opened to .080" and theirs ran with 5.56 and wolf 223.
I really don't know where to begin with your post. One thing I can tell you is that you are too absorbed into the whole ejection pattern thing.
Put a buffer in there that will allow you weapon to function with the ammo you have or plan to use.
One thing i can tell you is this- DO NOT CRUSH YOUR GAS TUBE OR USE AN ADJUSTABLE GAS BLOCK.
With a mid length you shouldn't really need more than an H buffer. With your 10.5' unsuppressed you should be able to run it with an H2. Forget that silly Spike's ST-2 nonsense.
With your 10.5' unsuppressed you should be able to run it with an H2. Forget that silly Spike's ST-2 nonsense.
I'm going to be shooting 5.56 almost all the time. I shows signs of being overgassed even shooting underpowered wolf 223 with a Xtra power spring and a H3.... and you think I should switch it to a standard spring and a H2 :confused:.
I think I'm going to take pull gas block and measure gas port.
Iraqgunz, why no adjustable gas port? I am looking at a Noveske CQB with a Switchblock for suppressed use. Not always, but thre are times when I will want the can. I don't build them, just shoot them, so give me your thoughts on it...Thanks.
I hope this isn't a hijack, but it sounds pertinant.
If it was overgassed you'd have ripped case heads, possibly blown primers, extractor marks, ejector shearing. Because the bolt is unlocking too soon.
A Noveske Switchblock is designed to do something particular and I would have no problems using one.
I am referring to those gimmicky adjustable blocks.
Iraqgunz, why no adjustable gas port? I am looking at a Noveske CQB with a Switchblock for suppressed use. Not always, but thre are times when I will want the can. I don't build them, just shoot them, so give me your thoughts on it...Thanks.
I hope this isn't a hijack, but it sounds pertinant.
Ryan,
Who makes the 10.5"? Having looked a little closer I think both of those are way to big (gas ports). My BCM 11.5" is nowhere near that saize and a middy shouldn't be that big either (AFAIK).
So I guess I would talk to whoever makes or sold them and ask WTF.
If you are going to keep them then you may want to look at the Vltor A5 system.
To be honest I could care less about ejection patterns. I want an AR that will work with the ammo I have and so far after 4000 rounds mine does.
I'm going to be shooting 5.56 almost all the time. I shows signs of being overgassed even shooting underpowered wolf 223 with a Xtra power spring and a H3.... and you think I should switch it to a standard spring and a H2 :confused:.
I think I'm going to take pull gas block and measure gas port.
You can fine tune your ejection pattern with extractor tension and ejector spring length is you're really intent on painting a pretty picture. As long as the upper is reliable, it really doesn't matter where the brass is going.
Belmont31R
03-18-11, 01:01
You can fine tune your ejection pattern with extractor tension and ejector spring length is you're really intent on painting a pretty picture. As long as the upper is reliable, it really doesn't matter where the brass is going.
Cutting extractor springs?
Cutting extractor springs?
Actually it's the ejector spring that gets cut. You can play with the extractor tension by using different springs or 'O' rings. Rifles usually need more extractor tension then less, but too much tension effects ejection. You can tune the ejection to drop the brass right next to you, or let the rifle throw it as far away as possible. As long as my upper is reliable, I don't try to tune anything.
Cutting extractor springs?
There was a document that Remington put out with steps on how to do this.
IMO, the ejection pattern thing is way over played.
To the OP, what symptoms are telling you its overgassed in particular?
The buffer and spring system in your gun is there to ensure the reliable functioning of your gun and longevity of its parts.
It is not there to tailor the recoil to your pleasure or to fine tune the ejection pattern.
The buffer and spring system in your gun is there to ensure the reliable functioning of your gun and longevity of its parts.
It is not there to tailor the recoil to your pleasure or to fine tune the ejection pattern.
So lightest combination and heaviest combination all function 100%, its not like buffers and springs are expensive, I just like to pick the combo that functions smoothly and ejects cleanly. I'm going to run each on a selectfire slower sometimes, so setting it up so its smooth and has slower rate of fire is fairly important.
I was surprised that a 10.5" with standard colt sized gas port (.093") could not be tamed, even with the lowest power 223 load I could find, even with heavy spring and H3 buffer. And the 16.5" with a .085" gas port that I would think would be overgassed, is behaving like has a much smaller gas port. Just looking for answers.
eternal24k
03-18-11, 11:48
Did you actually measure your gas port? where did you get those numbers?
Scotty,
The OP continues to mention a 10.5" barrel with a Colt standard size gas port of .093. Does that sound right to you? I was under the impression that it was smaller than that.
I think I read somewhere it was around .070-073. Doesn't .093 seem a tad bit large?
The buffer and spring system in your gun is there to ensure the reliable functioning of your gun and longevity of its parts.
It is not there to tailor the recoil to your pleasure or to fine tune the ejection pattern.
I don't know what the gas port is on a real MK18 barrel as nobody has removed the front sight base from one because they are too expensive and collectable.
Does it stand to reason that the stated gas port size sounds way too large?
I don't know what the gas port is on a real MK18 barrel as nobody has removed the front sight base from one because they are too expensive and collectable.
that would be huge. way too big. that's at the upper end of sizing for a 20" gun. but colt's done plenty of experimenting over the ages- maybe it's an old CQBR barrel? i cant verify it personally, but i was under the impression the mk18 barrels are at .070
OP- was the barrel chopped down from a longer barrel?
Ryan - which Nordic do you have? Just to give you something to compare to, I have the Lilja one - when I was running an M4 style stock, I was using a Sprinco standard (Blue) spring and a carbine buffer. No problems with a bunch of different ammo with the exception of Tula which occasionally failed to pick up the next round and lock back on firing the last round (it really is weak). PMC did work fine. I now have a rifle stock/buffer/spring in there - same results with that - everything fine except the occasional hiccup with that Tula shit....but thankfully I have now shot it all and won't be buying it again - if I want cheap ammo for close up practice, I'll stick with my usual Brown/Silver Bears. The rifle is a very nice soft and accurate shooter; ejection pattern is 3:30-4 Oclock. Did not measure my gas port, but given Liljas quality I doubt it is anything other than what it is supposed to be.
Iraqgunz, why no adjustable gas port? I am looking at a Noveske CQB with a Switchblock for suppressed use. Not always, but thre are times when I will want the can. I don't build them, just shoot them, so give me your thoughts on it...Thanks.
I hope this isn't a hijack, but it sounds pertinant.
The adjustable gas blocks I looked at use a set screw that needs an allen key to adjust. Carbon build up will freeze up the set screw. Combine that with the fact allen heads are not very durable, the adjustable gas block will, in time, become a non-adjustable gas block. Also, the hole for the set screw is another potential path for gas leakage.
Switch blocks are not really "adjustable". They simply have three settings- Normal, for shooting without a suppressor; Suppressed and Off
Did you actually measure your gas port? where did you get those numbers?
Scotty,
The OP continues to mention a 10.5" barrel with a Colt standard size gas port of .093. Does that sound right to you? I was under the impression that it was smaller than that.
I think I read somewhere it was around .070-073. Doesn't .093 seem a tad bit large?
I am going to try take it apart and measure, I did not before install. My numbers are from the manufactors.
Colt's milspec gas-port sizes are: 10.5" .093" 11.5" .081" 14" .063" 16" .063" - This is what I've seen on this forum, and other ar-15 related forums. At the time I ordered it seemed like everywhere someone was posting something along the lines of, ~"you should follow Colt sizes, 223 and 5.56 with all cycle that way, etc". I realize this is to much gas. I know BCM, Rainer, Noveske, LMT run smallish gas ports but Colt and most othere commercial vendors I thought just followed Colt's sizing. I was not expecting even wolf 223 to bounch out front of deflector with a H3 and Heavy spring.
Ryan - which Nordic do you have? Just to give you something to compare to, I have the Lilja one - when I was running an M4 style stock, I was using a Sprinco standard (Blue) spring and a carbine buffer. No problems with a bunch of different ammo with the exception of Tula which occasionally failed to pick up the next round and lock back on firing the last round (it really is weak). PMC did work fine. I now have a rifle stock/buffer/spring in there - same results with that - everything fine except the occasional hiccup with that Tula shit....but thankfully I have now shot it all and won't be buying it again - if I want cheap ammo for close up practice, I'll stick with my usual Brown/Silver Bears. The rifle is a very nice soft and accurate shooter; ejection pattern is 3:30-4 Oclock. Did not measure my gas port, but given Liljas quality I doubt it is anything other than what it is supposed to be.
I have both. Manufactor states both are .085". With a standard spring and H buffer it runs 223 and 5.56, with a ST-2 223 is unreliable and 5.56 runs 100% in semi, I've dumped a mag in a selectfire lower (with a H2) and it ran at least that one mag fine in auto. They are great, accurate, and very soft shooting. I have the end result I want with these, but I just don't understand WHY. Shouldn't the gas port in a midlength need to be down to .056-.063 to act like this? Shouldn't a 16.5" midlength with a .085" port act more overgased than a .093 10.5" carbine that has shorter dwell time and only a slightly larger gas port.
According some searching I did I came up with smaller numbers for the Colt port. I have sent an email out to get some further information.
My take on it is this. Pick the buffer that allows your weapon to function reliably without malfunctions or ripped cases and drive on.
I am going to try take it apart and measure, I did not before install. My numbers are from the manufactors.
Colt's milspec gas-port sizes are: 10.5" .093" 11.5" .081" 14" .063" 16" .063" - This is what I've seen on this forum, and other ar-15 related forums. At the time I ordered it seemed like everywhere someone was posting something along the lines of, ~"you should follow Colt sizes, 223 and 5.56 with all cycle that way, etc". I realize this is to much gas. I know BCM, Rainer, Noveske, LMT run smallish gas ports but Colt and most othere commercial vendors I thought just followed Colt's sizing. I was not expecting even wolf 223 to bounch out front of deflector with a H3 and Heavy spring.
jonconsiglio
03-18-11, 20:36
.093 is on the large end of the 10.5" spectrum. Colt, as I remember, uses .093 (should say it was .9x, this was during research when having a barrel cut, not sure if they do things differently with commercial and LE/mil for port sizing) for these barrels. Obviously you need to go up in size as we go shorter, but this is on the borderline of over gassed.
I no longer have my LMT 10.5" to measure for comparison, but I'll be working on a Mk18 clone, so I'll need to keep this in mind.
ETA 2 - I'd give the Vltor A5 and their heavier buffers a try. This may help a bit. I've had great results, as limited as that time is so far.
Jonathan
This is dangerously close to what I consider "range minutia".
The topic of ejection "pattern" is somewhat interesting. Once upon a time the location of spent brass was meant as a check for whether or not the rifle was "function[ing] reliably without malfunctions or ripped cases" and would continue to do so over time. Unfortunately, as is seeming too often the problem, it got stated, and re-stated, and a graphic was produced, and next thing you know it was an end-state.
This is the graphic. Note that location of brass is being used as an indicator of proper function, not as a tool to locate your bucket to catch brass for reloading.
http://i134.photobucket.com/albums/q111/rob_s/gun%20stuff/37688d1297901866-m-p15-st-t2-spikes.jpg
Should this be normal after ~30-50rd?
Should this be normal after ~30-50rd?
I just pulled out my 11.5 with a LaRue low profile gas block and I don't see any signs of leakage, on the barrel or the tube. Of course the rail could be obscuring some leakage but there certainly isn't much, nothing like you show. It's had 1950 rounds through it.
What I did see was that one side of my gas block has rust on it, that's interesting, it's stored in a nice dry safe and has actually been shot out doors a couple of times. Something else to deal with, oh well.
Should this be normal after ~30-50rd?
that's pretty leaky. if it was mine, i'd be investigating. you should really start a new thread, though.
ETA-
oops... didn't realize this was YOUR thread. my bad.
how's the block attached? looks like a set-screw-on-the-bottom deal... are you sure the screw was tightened down all the way?
Ok, I reached out to someone in the know and I was told that the correct gas port size for a Mk18 barrel is .067. At least that is how they come from Colt.
Should this be normal after ~30-50rd?
On both of my own rifles (and seen on numerous others) there is a fair bit of carbon build up on the tube where it goes into the gas block (extends about an inch and a half or so), and a little bit on the top of the gas block seat. Doesn't ever seem to get much worse though; as you shoot I believe they tend to seal themselves up (some higher mileage tubes can require quite a bit of effort to remove them from the block, which sort of proves that point). Not personally seen any out the front of the gas block though, although I have read that it does happen. Of course there will also be carbon on the rear where the tube goes into the carrier key (as per your pic 3)....that is pretty much the nature of the beast.
If you are concerned, when you put it back together you could always use a little loctite (green loctite 290 I believe is the preferred one for this) to effectively bed your gasblock, which should help take care of any leaks you may have.
I do understand you wanting to get to the bottom of this...but to be honest, if, as you say, you've got the result you want from the barrel/rifle, and its shooting accurately and softly, I'd put it back together really well (cleaning/degreasing/loctiting if you deem it necessary), and then go shoot it and not worry about it again!! :)
If you are concerned, when you put it back together you could always use a little loctite (green loctite 290 I believe is the preferred one for this) to effectively bed your gasblock, which should help take care of any leaks you may have.
WTF??!!
You do know that if your receiver extension doesn't fit you can use an angle grinder on it....just saying.
Where did you get the gas block from? If it's a quality block and barrel, and they fit together snugly, this may be very well be another result of the gas port/pressure problem.
Don't "bed" it with locktite.
WTF??!!
You do know that if your receiver extension doesn't fit you can use an angle grinder on it....just saying.
Where did you get the gas block from? If it's a quality block and barrel, and they fit together snugly, this may be very well be another result of the gas port/pressure problem.
Don't "bed" it with locktite.
Did you even look at his pictures, or read what he was asking and what I was replying to?
Regarding bedding the gas block, read post #4 in this thread for a start....and there are others. It is an accurizing trick, but if he is concerned about gas leakage, serves the same purpose. Think before you "WTF" the somebody next time.
https://www.m4carbine.net/showthread.php?t=4783
It is an accurizing trick
Voodo.
If your gas block doesn't fit snugly to your barrel, locktite is a less than ideal solution. By far.
On all of the Noveske or Daniel Defense barrels i've owned, and espically the Noveske ones, the gas blocks were very hard to slide on. As such, one could surmise the fit between the two was tight, and i've never had any leakage problems even close to that.
Some is normal. It may even be more noticeable -visually, on a bead blasted stainelss barrel, as opposed to a phosphate one.
Either way, locktite is a band aid and not a fix.
The block sealing itself may be why the ejections results didn't seem to improve or even got worse as heavier springs and buffers were added, maybe block geting more and more sealed. The barrel has polygonal rifling that may increase the gassing also. If I get the block sealed perfectly my gas situation may be worse than it is now also. You can rock the gas block very slighly when it is on barrel, I remember my other barrels they fit tighter or I had to tap them a little to get on.
I've never had a gas block that had any movement to it when installed. As a matter of fact, on my most recent Noveske/MSTN barrel, I had to apply a little force to slide the gas block on. It was fitted very tightly.
Did the block come with the barrel or was it purchased separately?
Ok, I reached out to someone in the know and I was told that the correct gas port size for a Mk18 barrel is .067. At least that is how they come from Colt.
This sounds about right. I have an e-mail into Colt to double check.
C4
The 2 Colt Mk18 barrels that I run are 10.3" and I have been told that they are .070 gas port openings. I have not pulled the FSB and measured them however. I will say that as a replacement barrel on a standard M4A1 they both have run 100% for several thousands of rounds without any other changes.
Edit - I will add that the original topic makes my head hurt. As in good grief hurt.
Regarding bedding the gas block, read post #4 in this thread for a start....and there are others. It is an accurizing trick, but if he is concerned about gas leakage, serves the same purpose. Think before you "WTF" the somebody next time.
https://www.m4carbine.net/showthread.php?t=4783
Ok, I read the thread, and I still don't get the locktite thing. Is there a problem with low profile gas blocks and proper sealing? I'm asking because I've been shooting high power for over ten years, and have never heard about someone having to 'bed' their gas block for a proper seal.
I've never had
Unless you can expand on this in a way that makes it worthy of technical consideration (meaning a substantial increase in the sample size that results in refuting and invalidating the practices and experiences of recognized subject-matter experts who have posited diametrically to your opinion...), you should probably just stop right there.
DirectDrive
03-21-11, 12:24
You can rock the gas block very slighly when it is on barrel, I remember my other barrels they fit tighter or I had to tap them a little to get on.
After finding that, the next thing I would do would be to mic the barrel OD and the gas block ID to see what was up.
Ok, I read the thread, and I still don't get the locktite thing. Is there a problem with low profile gas blocks and proper sealing? I'm asking because I've been shooting high power for over ten years, and have never heard about someone having to 'bed' their gas block for a proper seal.
You're probably better off asking that in the linked thread, as its moving OT for this one - I only brought it up in the context here because it may have been some help in serving as a dual purpose (i.e. accurizing, with the inevitable sealing improvement as an interlinked benefit). Robb (who posted it originally) would be able to give you a far better explanation. It makes sense to me, as I once had a v. stringing issue that was cured by using a bit of blue loctite on the barrel extension - this gasblk bedding seems to be an extension of that principle).
Verified with Colt. MK18 barrels (official ones that go to the USN) use .070.
LE 10.5" barrels might have a SLIGHTLY larger GP size.
C4
Unless you can expand on this in a way that makes it worthy of technical consideration (meaning a substantial increase in the sample size that results in refuting and invalidating the practices and experiences of recognized subject-matter experts who have posited diametrically to your opinion...), you should probably just
stop right there.
Not everyone on the forum is going to work in an armory. I thought my post(s) made it clear that my view was the result of my experience, which pertained directly to the two brands I had listed.
I’ve actually spent a lot of time now trying to research and published/posted writings on bedding a gas block on an AR15. The only posts I’ve found (2), on this forum no less, have been from Robb, and are three to four years old.
This is not a slam on Robb…but it hardly seems to be a standard industry practice. If he has good results, then press on.
I’m not telling someone not to do something that would appear in a TM for instance, where whatever practices are well documented.
I'm thinking about having it welded and redrilled or using a adjustable gas block.
I got my number from SAW. If I were a betting man I would say that the .070 is the LE size. I know I was told that they are opened up for the LE market to ensure that they function reliably with the different loads available.
Verified with Colt. MK18 barrels (official ones that go to the USN) use .070.
LE 10.5" barrels might have a SLIGHTLY larger GP size.
C4
EzGoingKev
03-21-11, 21:45
This is a page from a Power Point presentation that says it is from Crane.
https://lh3.googleusercontent.com/_Kybyq3n1q3w/TYgMonq0uzI/AAAAAAAADjg/T8HjGzgyKDw/s800/Crane%20SBR_017.jpg
Should this be normal after ~30-50rd?
RyanS,
All of my Noveske SS barrels look the same as yours. They will seal up after a while. Don't get to wrapped around the axle about a little leak. It shows up more in the SS because their light colored. The black guns do it as well.
As far as extractor/ejector patterning goes, I run the heaviest buffer that will function the gun with the rifle shot off contact with the shoulder. This was I know that the gun will function off shoulder in situations where the gun is not in hard contact with the body IE: the old HK MP5 CQB tight sling method.
If your never going to roll around on the ground or shoot from crappy positions then disregard and run what you like.
NOW GO SHOOT THAT GUN with it's huge gas port. 50 rnds, god, I wish I owned a gun with ONLY 50 rounds through it :-)
Until that day,
Darkop
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