Need HELP! Gas system issues.

[Longhorn86]

I'm new here to M4Carbine, I was referred by a friend and I'm so glad he did, I have done a lot of reading.Thanks guys for all the hard work. Now to my question. I have an decent quality 14.5 upper made by a local guy (NC). I'm running a AAC M4-1000. I have blown 2 sets of gas rings in 1000 rounds(Rem). I bought the solid one piece gas ring and it has worked so far but the brass are black when they come out. There is no resistance between the bolt and the carrier though and I don't think that's cool. I can't tell what the buffer is either, I can't see any markings. I talked to the guy who made the barrel and the gas port out of the barrel is .0072 he said that if I brought it back he would make it .0082 (which is what he doing now to newer ones). I don't know if that is the answer or not and I'm not experienced enough using suppressors to make a call. I would also like to have the real MIL-Specs so I would know buffer size and gas port hole size etc. Any ideas?:suicide2:

[Eric D.]

WHAT? I hope this is typed wrong. .072 is more believable but still a little big for that barrel, even more so being suppressed. The gun would not run at all with a gas port 7 thousandths wide.


I talked to the guy who made the barrel and the gas port out of the barrel is .0072 he said that if I brought it back he would make it .0082

What exactly do you mean by "blown gas rings"? What brand of bcg are you using?

There should be resistance between the carrier and bolt. If you set the assembled bcg upright on the bolt face, with the bolt pulled out, the bolt should not retract under the carrier's own weight.

If you have access to a small scale, weigh the buffer and someone can tell you what it is. Typically, H3's are unmarked but my H3 from g&r is indeed marked as such.

I don't recall mil spec gas port size but most barrels on the market won't adhere to it anyway. The reason is that that the military exclusively shoots 5.56 NATO pressure ammo. An average joe shoots everything from shit silver bear to actual 5.56 ammo so the gas port needs to be larger to accommodate the ammo usage of the end user.

[bp7178]

How do you know the gas rings are/were blown?

When suppressed, most of the fouling is coming back through the barrel. The can is still under pressure when the bolt carrier group starts moving. When the case is extracted, this pressure rushes down the barrel. This is more than likely the cause of the black brass. I would assume this doesn't do it w/o the can.

I was just going to address the gas port thing. .0072 is pretty small... .072, not as much... ; )

RRA buffers arent marked, at least the ones I've seen sold in my local shop. The vast majority on the market are. With a suppressor, I would probably at least run a H2.

[Longhorn86]

The guy I bought it from said he called his engineer and he told him the hole was 72 thousands and he could make it 82 thou. When I say blown I mean they were distorted and out of the groove on the bolt. Upon removal and inspection they weren't round any more or flat. I just put in Mcfarland one piece ring from Fulton Armory. I realize that the bolt was supposed to have resistance to the carrier but to be honest at this point I figured they new more than I did. The lower is a Bushy from a carbine model. I see H, H2 etc. can I weigh them and tell the diff?

[Longhorn86]

Oh, the BCG is the same as the manufacture of the Upper. Now the I have a registered SBR I may end up ordering a new upper if I can work this out. A little background, the guy I buying from is a local guy the has been in bus. for years. He shopped around until he could get a shop to make his own brand of AR. I think I got one of the first made, lucky me, he won't tell me who's making them. And yes without the can the brass aren't black. I figured it was from the ring. I even tried some hand loads before this with min. load to see if my rounds were to hot. Just trying everything.

[Eric D.]

This is a red flag IMO


Oh, the BCG is the same as the manufacture of the Upper... he won't tell me who's making them.

This is definitely a problem. I would imagine that the rings are jumping out of the groove because of this extra space. The quality of the bcg is definitely suspect, I would get one of know quality from bcm or dd and I'll bet that will fix your problem. Could you post some pics of the bcg and the damaged rings?


There is no resistance between the bolt and the carrier

ok, 72 thou is better, but like I said, still a little big. See how the McFarland holds up, i know some of the industry professionals here will advocate their use. If you want to go back to gas rings, get a good set from BCM or DD.

If your scale measures to at least tenths of an oz, yes you will see the difference.

[Longhorn86]

I found some pics on the site that give the specs for all the buffers. The lower is going to get if it doesn't have an "H". We'll see about the ring, I don't know about there not being any resistance there, it worries me a little. It sounds like I should leave the gas hole diameter alone. Thanks for the help. :D

[MistWolf]

72 thousandths = .072
.0072 = 72 ten thousandths

[Iraqgunz]

I am trying to make sense of this post and honestly I can't.

1. If he won't tell you the maker of the upper and BCG you really need to take it back.

2. 072 isn't terribly huge, so I would leave it alone.

3. I cannot for the life of me figure out how you are "blowing" gas rings.

4. In any case this thing sound like a POS and I would take it back and get a known QUALITY upper- BMC, LMT, Colt, Noveske, or DD.

[Quentin]

I'm glad I'm not the only one having trouble understanding the OP.

I bet the gas port is already larger than .072. Did you try the H2 buffer yet?

[Todd.K]

Carbine or mid gas system?

[Rmplstlskn]

I am trying to make sense of this post and honestly I can't.
<snip>
4. In any case this thing sound like a POS and I would take it back and get a known QUALITY upper- BMC, LMT, Colt, Noveske, or DD.

I concur... Seems like multiple quality issues with rabbits running in holes in all directions... all based on the words of the "builder."

Rmpl

[C4IGrant]

Gas port on a 14.5" M4 should be .063. If you are shooting suppressed, then you are basically doubling your gas. If the gun is over gassed to begin with (which yours is), then you will experience all kinds of broken parts and or parts wearing out faster than normal IMHO. Not to mention a lot more felt recoil.


I would abandon ship if it was my uppers.



C4

[Evil Bert]

If the Builder will not tell you who makes the upper and the BCG (which sounds fishy to me), it is likely because he is using a very cheap upper assembly or assembling it from cheap non-quality parts and selling it to people like you who fall victim for the support your local shop. I support this on certain things and only when the local guy offers known quality. If the Gas Port is .072, then it is what many would consider over-gassed to fire the cheap .223 brass and steel cased ammo. Something like a DPMS, Stag, RRA, Bushmaster, Del-ton, etc. that are over-gassed to ensure functionality with nearly all types of ammo.

I bet if you ask him if he built you a mil-spec rifle, he will tell you yes. If he does, you know for a fact he has no clue on what he is doing. The TDP does not call for a .072 port.

In any case, the .072 port is not the end of the world and is certainly usable. You BCG is hosed. Toss it and get a DD, BCM, LMT, Noveske, Colt, etc. (i.e. known quality). Then test it out. If you think it is still recoiling a bit harder than it should be (because of the port size) then get a VLTOR A5 recoil system.

[eightmillimeter]

Gas port on a 14.5" M4 should be .063. If you are shooting suppressed, then you are basically doubling your gas. If the gun is over gassed to begin with (which yours is), then you will experience all kinds of broken parts and or parts wearing out faster than normal IMHO. Not to mention a lot more felt recoil.


I would abandon ship if it was my uppers.



C4

Grant when you say "doubling" the gas you mean just the length of time of the gas impulse, not the force itself right? Or is it a little of both. No secret suppressors are hard on them.

[Longhorn86]

Yea, I guess as a whole I hearing what I already knew. Get rid of this POS and buy a quailty upper. I can't figure out the gas ring thing either. I've had and worked on AR's since I was 14yrs. old. back when a new Colt was 400 bucks! Anyway, I'll cut my loses and move on.

[Heavy Metal]

0.72 on a carbine gas system using a Can?


WWWWWAAAAAAYYYYY over-gassed!

The only thing that could salvage that is a LMT enhanced carrier and a much heavier buffer.

[markm]

If the guy wants to open the port more... he CLEARLY has no clue WTF he's doing.

You should be running an H2 or H3 buffer to reign that already over gassed Mo Fo in a bit.

[Mr. Goodtimes]

This is why I don't buy local. Knights is the only "local" Florida company I would buy a rifle from.

Call me a gun snob but I've given up on the small local guy building rifles, because usually he's some bubba like the retard that put together the OP's rifle. If I buy a rifle it's going to come from a reputable manufacturer. There are too many local fly by night AR makers these days.

[Travis B]

Is it possibly a MMC gun? I have read pages and pages of bad reviews for their stuff; they're without a doubt the worst NC manufacturer. But then again, there aren't any great ones.