Eliminate or reduce gas blow back?

[User 1234]

The official Army and Air Force maintenance manuals both direct the user to ensure the gaps in the three gas rings are not lined up. Whether it would actually make a difference I don't know.

 

[bikemutt]

An adjustable gas block will allow you to set the amount of gas to the minimum needed to reliably cycle the action to the absolute minimum. Once it's installed it's very easy to find that perfect setting. My preferred block is from SLR Rifleworks as others have mentioned. However, if you have not built an AR from the ground up, replacing a gas block may be a daunting task, if it was my first time, I'd have a gunsmith do it.

I've have less success minimizing gas blow back with other methods like silicone sealing the charging handle area, replacing the forward assist with a plug, etc. Once the gas gets into to the action it has to go somewhere, if it can't bleed from one place it will bleed from somewhere else.

Another thought is to consider trading for a piston rifle which keeps the gas out of the action to start with. That sort of system still uses gas pressure to cycle the action but instead of having it all happen down by the bolt, it occurs up near the gas block, much further from your face. A secondary benefit is the action tends to stay cleaner.

I'm particularly sensitive to the acrid gas from semi-auto rifles, if my goal was to use one as an ammo hose, I'd go with a piston AR.

 

[Member 34319]

I think I was in @OregonArmsAmmo while you were @Yvette ... sounds like they got you taken care of with a higher power scope and adjustable gas block.

 

[titsonritz]

The official Army and Air Force maintenance manuals both direct the user to ensure the gaps in the three gas rings are not lined up. Whether it would actually make a difference I don't know.

Yes it does and it is still BS. Find an older addition and it will state the barrel nut torque spec is 30-80 in.lbs. it was a typo and fixed in later additions. Also the method of staking the carrier key is an outdated and nothing I would do. I have multiple copies of TM 9-1005-319-23&P and do use it, to point but there are some errors and/or dated information in it.

Regarding the gas rings, if you remove the bolt from the carrier and look past the gas key through the cam pin shaft hole, slightly to the rear you'll see a shelf and notice the bolt path is not perfectly cylindrical, it is slightly tapered, this taper causes the rings to be pinched together and closes the gap. In fact, a properly built AR will run a single gas ring or none at all in the case of a suppressed weapon.

 

[titsonritz]

 

[WhyElKay]

Pretty nil, what BCG did you change to?

Pretty nil, what BCG did you change to?

Fail Zero BCG

 

[titsonritz]

I know a lot of people recommend and use an adjustable gas block, I have no use for them. They introduce additional and unnecessary complexity to the gas system, which, other the mags and ammo (neither of those have anything to with the gun), is the number one issue facing AR's. If the barrel was properly ported in the first place there would be no need. Once again, they are another bandaid approach. There is an entire industry that exists thanks to sub-par AR components.

I can tell you with 100% certainty SIONICS supplies dozens of LE departments with suppressed weapons without adjustable gas blocks. I was in an armorers class last month, the instructor (Will Larson, God rest his soul) stated the same thing. He was their master armorer.

 

[WhyElKay]

I think I was in @OregonArmsAmmo while you were @Yvette ... sounds like they got you taken care of with a higher power scope and adjustable gas block.

Yes they did! I'm working on putting the adjustable gas block on now

 

[3MTA3]

@3MTA3 this reminds me.
I really only have an issue with the gas after a few mag dumps, and I believe it is the oil boiling off.

My Ruger didn't have any issues blowback or otherwise when I "proofed" it which involved several mag dumps. Something I do with any weapon that I might use for defense.

ot
I'm just going to throw this out there... I've taken it apart and cleaned it. I've changed the bolt carrier group and I've changed the charging handle. What is the possibility that I did not put something back together correctly? Several of you guys say you have no issues with this.

I'm in agreement with @titsonritz . These are designed so soldiers in lousy and stressful conditions can field strip, clean,maintain, and reassemble. If it fits it's pretty much right.

 

[titsonritz]

Fail Zero BCG

I was afraid of that. While this has nothing to do with your issue, Nickle Boron is not a good thing on bolts. The process embrittles steel often resulting in sheared lugs, I've seen multiple just flake off the finish.

 

[Member 5605]

Convert to a piston system.

 

[titsonritz]

Convert to a piston system.

No way.

The truth is a standard AR design is a piston system, the carrier is the cylinder and bolt it the piston (with rings on the tail). The in-line gas system is part if the AR's genius. If you want a traditional piston system get an AK.

 

[308]

I know a lot of people recommend and use an adjustable gas block, I have no use for them. They introduce additional and unnecessary complexity to the gas system, which, other the mags and ammo (neither of those have anything to with the gun), is the number one issue facing AR's. If the barrel was properly ported in the first place there would be no need. Once again, they are another bandaid approach. There is an entire industry that exists thanks to sub-par AR components.

I can tell you with 100% certainty SIONICS supplies dozens of LE departments with suppressed weapons without adjustable gas blocks. I was in an armorers class last month, the instructor (Will Larson, God rest his soul) stated the same thing. He was their master armorer.

SIONICS is supplying the weapon pre-suppressed? If that is the case then they most likely dialed in the gas port hole for a suppressed rifle...correct?

 

[bikemutt]

No way.

The truth is a standard AR design is a piston system, the carrier is the cylinder and bolt it the piston (with rings on the tail). The in-line gas system is part if the AR's genius. If you want a traditional piston system get an AK.

The AR direct impingement gas system is a great design, no doubt about that. However, the OP is concerned about the acrid gas fumes which exit near the ejection port with that particular design. Some shooters are particularly sensitive to those gasses, some are not. And yes, DI is a "piston" system. However, a piston system in the non-DI sense simply replaces a gas tube with a push rod of sorts. This allows the design to control the direction and location of the exhaust gas, typically moving it further away from the operator's face and sending it it in more favorable direction. The typical piston AR is not beyond criticism of course, it introduces a new moving mass that some shooters allege interferes with accuracy and that sort of thing, but, in this case, it may solve an intractable problem for those who simply can't tolerate the fumes.

 

[WhyElKay]

I can't remember how this goes back on the install is it ONE OR TWO
ONE


TWO

 

[Pete F]

I agree with several comments about piston rifles. Since no gas is directed backwards, everything stays cleaner with no gas in your face. I have 2 AR type rifles and both are piston.

 

[Member 5605]

I can't remember how this goes back on the install is it ONE OR TWO
ONE
View attachment 603286

TWO

View attachment 603292

Grab buffer tube end, shake the other end towards the ground. Cam moves forward along with bolt and perfect alignment to put back into upper.

If you are referencing the cam pin, it only goes one way as the firing pin goes through the center of it.

 

[Caveman Jim]

I had an Adams Arms piston kit installed and have never looked back... It runs smooth and the chamber is A LOT cleaner.

 

[osprey]

I can't remember how this goes back on the install is it ONE OR TWO
ONE
View attachment 603286

TWO

View attachment 603292

I fail to see any difference in photos but neither one will work as you must pull bolt out all the way to re-assemble

 

[Steel Head]

The old gas buster charging handle was made for just that purpose

Lots of the newer designs use the same kind of design elements to do the same.

It appears your optic is mounted on the hand guard
That can cause problems.