6 ARC Gas Block Issue -- Need Help

[Louisiana Shooter]

Clamp on gas block if you're not already using it. It seals much better.

 

[Gargoyle]

AA2520 plenty dirty.

 

[SG4247]

Thats a good one too! ^^^^

 

[Ray123]

Like I said earlier all I really wanted was an opinion on a dirty powder. But here is the info on the gun and the problem
here is the build -

22" barrel by Precision Firearms, Aero upper, Aero BCG and bolt, Aero handguard, Aero adjustable gas block, Odin Works carbine adjustable buffer , Rifle + 1 gas tube

First lower is a older Rock River Match, the second is a newer Palmetto Armory. Both lowers work fine on a pair of Grendels and a .223

what I have tried so far

As far as the gas block goes I have uninstalled and reinstalled at least 5 times, when I reinstall I use a borescope looking up through the gas port in the barrel to make sure it is perfectly aligned. From that perspective it looks like the barrel gas port is larger than the gas block port. The two setscrews are torqued to 30 inch pounds IAW manufacturer instructions. I have went from 1.9 oz on the buffer to 4.2 or whatever the three tungsten's are. At the moment it is 1.9. Gas block is fully open @12 clicks

Upper has been mounted on 2 lowers, and I have tried both a BobSled and 2 brands of magazines all of which of which work perfectly with other uppers. I have also tried 2 other BCG's and bolts again all BCG's work perfectly in my two Grendels. It feeds perfectly from different magazines and with just the aluminum weights in the buffer and gas block wide open it is acting as if it is over gassed with the ejected cases landing between 3 o'clock and 2 o'clock instead slightly behind at 4 - 5 oclock.

The only time it has locked back was the first 20 rounds after I wicked some blue LocTite in around the gas block and let it cure for a day. That was with both magazines and Bobsled. Yesterday when I went back to the range it once again started the same old behavior refusing to lock back after the last round. I am 99% sure the heat from the gas melted the loctite and pushed it out, which I assumed would happen. That gas is a lot hotter than any flavor of loctite. The only reason I tried it to was to nail down the problem to gas block leakage which it did.

The carbon trick has worked for me twice before, once on a home grown .223 the other a custom built 6.5 Grendel upper by a well known builder. He was the one that first turned me onto that trick. It works, I have seen it cure the problem twice. I am going to try the graphite trick A Marsh suggested and if that does not cure it in 30 or so rounds I will be ordering another gas block, it that does not cure it I will be sending the barrel back and see if the maker can figure it out

So I ordered a complete upper from Areo Precision. The only way to get into 6 mm ARC at the time ..I learned my lesson, never again!
After several range trips ...
Took out the barrel and gas block and scrapped both. It shot 2" to 2.5" groups. I have the scrap Areo barrel...just checked the gas port dia is .096" #41 drill..probably opened up. I usually do.
Do yourself a favor Order a Proof Research barrel and a Superlative Arms adjustable gas block...it will shoot .5" 5 shot groups ...with standard carbine buffer and spring and works 100%. This gas block IS set .025 back from the shoulder.
But if you insist on using this PITA the way it is ...open the gas port to .096" with a #41 drill.
Another is Green High Temperature Bering Sleeve Loctite ... but it's rather permanent. You can wax the inside of the gas block with Johnsons paste wax to help in removal... for desperate times& people.
But I'd just throw away the Areo barrel and gas block and get the good stuff, mentioned above...it works with standard carbine buffer & spring ... and is very accurate. I scrapped Areo barrel right after I finished the Proof Research barreled project...took both ARs to the range the same day...the Areo shot 2.5" group with 108 match ammo, And the Proof Research shot its first 5 shots into .5" with the same ammo on the same day...Ordered another Proof Research barrel it it's slightly more accurate than the first ... these shoot fantastic.
But there's more to building an accurate AR than just assembling parts. Put 3 shots in the same hole .1" or .2" ...not a big 1" 3 shot group, occasionally, ...but mostly 1.25" to 1.5" ...don't work for me...functioning or not it just not up to my accuracy standards.

 

[Adam in WI]

That green sleeve retainer Loc-tite helps hold the cam gears on in the 15.0L Cummins ISX. It usually takes a fair amount of thermal and kinetic persuasion to release it.

 

[JimSC]

But I'd just throw away the Areo barrel and gas block and get the good stuff, mentioned above...i

reread my post, I don't have a Aero barrel.

On another note. I looked at my gas block and the barrel in front of it last eve and see no signs of any gas leakage at all. What keeps bugging me is the ejection pattern which indicates over gassing, not under gassing. Is it possible for the BCG to be traveling too fast ? Or maybe the bolt is binding a bit preventing it from catching on the empty magazine catch?

 

[Gargoyle]

Is it possible for the BCG to be traveling too fast ?

Yes. In an over gassed condition, the bolt can move too fast not allowing the brass to properly eject. One will get stove pipes, or the brass ejects only a foot from the rifle and forward.

 

[Walt Krafft]

Gas rube worn or mis-alighned? Carrier key bore worn? Carrier key leaking? Bolt tail undersize? Carrier bore oversize? Gas rings mis-aligned, worn, or broken? Magazine spring too weak or strong? Bolt stop spring too weak? Buffer too lite? Bolt carrier too lite? Buffer spring weak? Lots of things to get right.

 

[Drop Port]

reread my post, I don't have a Aero barrel.

On another note. I looked at my gas block and the barrel in front of it last eve and see no signs of any gas leakage at all. What keeps bugging me is the ejection pattern which indicates over gassing, not under gassing. Is it possible for the BCG to be traveling too fast ? Or maybe the bolt is binding a bit preventing it from catching on the empty magazine catch?

Absolutely, severe over gassed can / will cause several issues. When you say "ejection pattern which indicates over gassing" It's not an indicator, its telling you hey! slow this thing down, you have to know what you are seeing and correct for it.

 

[Drop Port]

Yes. In an over gassed condition, the bolt can move too fast not allowing the brass to properly eject. One will get stove pipes, or the brass ejects only a foot from the rifle and forward.

+1 When this happens most hobby builders assume under gassed because the empty case limps out of the ejection port, they couldn't be more wrong. Thus, the importance of understanding symptoms and what you are seeing before trying to make corrections.

 

[jelenko]

The first thing you should do is confirm whether it's a gas system or other component issue.
WOA has a write up of the test - very simple and quick.
From WOA's FAQ's:

How to identify a short cycling issue​

One of the questions we get a lot is “Why doesn’t my bolt lock open when I fire the last round in the magazine?” Here is a simple test to help you identify the cause.

• -A live round must be fired for this test so you must be in an appropriate location to perform this test.
• -Manually lock the carrier to the rear by pulling the charging handle to the rear and depressing the small tab on the bolt catch.
• -Insert one round into a magazine and then insert the magazine into the rifle.
• -Close the bolt by depressing the large tab on the bolt catch or by pulling the charging handle to the rear and releasing it.
• -While applying pressure to the small lower tab on the bolt catch, fire the round in a safe direction.

If the carrier locks to the rear with the bolt stop engaging the front of the bolt, then there is an issue with either the magazine or the bolt catch being used or the lower receiver. It is not a short cycle issue.
If the bolt does not lock to the rear or engages on the front of the carrier, then you do have a short cycling issue.

 

[Drop Port]

The first thing you should do is confirm whether it's a gas system or other component issue.
WOA has a write up of the test - very simple and quick.
From WOA's FAQ's:

How to identify a short cycling issue​

One of the questions we get a lot is “Why doesn’t my bolt lock open when I fire the last round in the magazine?” Here is a simple test to help you identify the cause.

• -A live round must be fired for this test so you must be in an appropriate location to perform this test.
• -Manually lock the carrier to the rear by pulling the charging handle to the rear and depressing the small tab on the bolt catch.
• -Insert one round into a magazine and then insert the magazine into the rifle.
• -Close the bolt by depressing the large tab on the bolt catch or by pulling the charging handle to the rear and releasing it.
• -While applying pressure to the small lower tab on the bolt catch, fire the round in a safe direction.

If the carrier locks to the rear with the bolt stop engaging the front of the bolt, then there is an issue with either the magazine or the bolt catch being used or the lower receiver. It is not a short cycle issue.
If the bolt does not lock to the rear or engages on the front of the carrier, then you do have a short cycling issue.

Bad advice, this is 101. Severe over gas will also cause the bolt to not lock back and by putting pressure on the bolt catch it will override and mask an over gas issue and force the bolt catch to grab.

 

[jelenko]

Bad advice, this is 101. Severe over gas will also cause the bolt to not lock back and by putting pressure on the bolt catch it will override and mask an over gas issue and force the bolt catch to grab.

What is the test to tell if it's overgassed?

 

[dellet]

In your original post, the problem was solved temporarily with Loctite.

In post #15 you stated that with the bore scope, the port on the barrell appeared larger than the port on the gas block..

Post #26, no signs of leakage.

Pull the gas block. There should be a perfect circle of carbon around the port in the barrel. If there is a leak, there will be streaks visible where the carbon is traveling. If there is no ring, the port on the barrel may be over sized.

This will be a perfect time to measure the port in the barrel. if it is larger than .125", then it is indeed larger than the mating hole in the gas block and needs to be replaced by the manufacturer.

The best explanation if all of the above is true, is that you actually plugged up the gas system with the loctite and it worked until it blew out.

But...
you should be able to correct the over gassing by dialing the adjustable block closed.

Have you tried that?

 

[Drop Port]

What is the test to tell if it's overgassed?

Not a test, a basic tune 101. Watch the ejection pattern 3:00 area straight out of the firearm is good. 1:00 over gassed, 1:00 with limp ejections at times, case falling next to the rifle, severe over gassed. Along with bolt not staying back on last shot.
We put suppressors on known Brand A, 10" guns and it tool nine ounce buffers to slow them down enough. Not the appropriate fix just a test, an adjustable gas block tuned properly was the cure.

 

[Gargoyle]

What is the test to tell if it's overgassed?

Over gassed guns will lock back on last round for sure. I look for:

Brass ejecting prior to 2:30
Ejector smears on case head
Brass just barely hopping out of the ejection port or stove pipes. (Means bolt operating too fast)

If I drill the gas port too big the only savior so far is a bleed off adjustable gas block, like Superlative Arms. Restrictive gas blocks don't help, even the restriction setting on the Superlative Arms doesn't help.

 

[jelenko]

Over gassed guns will lock back on last round for sure. I look for:

Brass ejecting prior to 2:30
Ejector smears on case head
Brass just barely hopping out of the ejection port or stove pipes. (Means bolt operating too fast)

So, what DropPort might have wanted to say is: First test if the rifle is overgassed.
His comment about 'Bad advice' wasn't very helpful.

 

[Drop Port]

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Go to the videos and see proper gassing, it's a good visual example. Mike is a friend and wealth of knowledge, with more patents than most in the industry. We ran a 10" gun so hard it wouldn't lock back at times, forced it to limp eject and stovepipe.

 

[dellet]

What is the test to tell if it's overgassed?

If you can't neck size only

 

[Minshooter]

The excellent advice to get a properly sealing clamp on adjustable gas block -is the place to start.

If this was already mentioned somewhere, sorry, I missed it, but:
I didn't see any mention to close the AGB down to 1/4 open or so, and then test while backing out
in not more than 1/2 turn increments. You may find a solution. Or, at least, can rule that out.

I had two identical model 18" 6mm ARC barrels. +1 gas tubes.
One would only run at about 5/8-2/3 open. One would only ran wide open.
Could not find the slightest dimensional difference.
Switched just about everything around; tried different powders, etc. same results.
(Settled mostly on CFE; not for function, but often was best accuracy)