PSA Adjustable Gas Block Questions.

[WSAR15]

I just bought a PSA lightweight 18" 6.5 G upper assembly. I seems quite nice. It has an adjustable gas block not too accessible. Before I take the hand guard off etc... maybe someone can give me directions.
It appears the adjustment screw is accessible on the front of gas block (as you look down the barrel). On the right side of the gas block (as you look down the barrel to the receiver) there is a small silver screw - it this to lock/unlock the gas adjustment screw?
Any idea who makes this gas block?
Thanks.

[A5BLASTER]

Yes smaller screw on the side locks the adjustment screw that is locates on the front of the gas block.

They will probably use two different allen keys, not to unlock and normally a lil bigger one to adjust.

[FRB6.5]

PSA says they make them.
The front screw is the gas and needs a 5/64" Allen wrench, flush with the front of the block is full open. The smaller stainless screw on the side is the lock screw it needs a .050" Allen wrench.
Be aware my lock screw was barely inserted and not tightened down at all, glad I caught that before losing it.

Additionally check your gas key on the carrier, mine was not torqued, thread locked or staked. Sadly didn't find that until it stopped cycling at the range.

EDIT:
A long 5/64" driver may be advisable over taking the hand guard off.
https://www.amazon.com/Bondhus-3704-Scre...XDBT8CV2TH

EDIT 2:
There are at least two models of gas block with different adjustments (and likely different bit sizes). The info above is for the front gas, side lock variant.
http://www.65grendel.com/forum/showthrea...post216165

[TraderRik]

Great info - thanks!

[Wanderson]

I never removed my hand guard to adjust, just ordered a set of 12” long Allen/hex keys.

Out of the box it’s set to max gas so it’ll run just fine without messing with it, but you will be amazed how much less it recoils just by taking a few minutes to dial in. And I didn’t dial mine to the ragged edge of operation, once I hit the spot where it failed once, I opened it back up a half turn. Haven’t touched it since.

[Dlbleak]

Do you recommend starting with an AGB? Talking with a friend that has built many guns. He said the Grendel was one of the most picky he’s dealt with.

[A5BLASTER]

Do you recommend starting with an AGB? Talking with a friend that has built many guns. He said the Grendel was one of the most picky he’s dealt with.

I haven't found it picky at all, I I'm willing to bet most haven't either.

I run adjustable gas on all my rifles but to be honest, it's just as easy to get one to run with a typical gas block and standard buffer and spring for the stock setup.

Have one 20 inch adjustable gas with a gen 1 scs, but can pull it and drop in a standard rifle buffer and spring and it runs just fine with no gas adjustment.

Have a 16 inch that uses adjustable gas and a standard carbine buffer and spring but can drop my gen 1 scs into it and it runs just fine with no adjustment.

What causes people issues is buying barrels with gas ports that are not cut to the correct size for the gas length and or buying a barrel with the wrong gas length.

[wiguy]

I am having some cycling issues with my brand new 18” PSA Grendel upper. I’m not surprised my higher/mid reloads had issues but just about the same with Hornady factory ammo. Right now not to worked up about it, will look at the magazine too.

Naturally I planned to look at the ‘adjustable’ gas block. The 1st issue is the set screw is so tight it’s been impossible to back out. My best fitting tool is an ‘Allen’ type wrench. I haven’t located a driver bit that fits to my satisfaction. So I’m dead in the water with checking the gas block. I’ll look around here or maybe go out tomorrow looking for a better fit.

I did make sure all was clean and lightly lubed before shooting.

On a better note it did seem to shoot fairly well at my 50 yard test site. Of course I had to clear malfunctions and help with the cycling.

[FRB6.5]

@wiguy the gas should be in the full open position out of the box, if the screw on the front of the block is flush, it is. Check the gas key on the bolt carrier, as I noted above, mine was not properly attached and loosened after a few rounds and caused cycling issues.

If you find yours has done the same, clean and de-grease the screws, key and carrier with non-chlorinated brake parts cleaner. Then put a light coat of high strength red loctite or other brand thread locker on the bottom of the key to act as a seal (Permatex gasket sealer can be used as well). Put some of the red loctite on the screws and torque to 56 inch pounds and let cure over night. Failing that contact PSA for an RMA if you don't mind the wait.

[wiguy]

Thanks FRB, I’ll look into all of those mentions. I have to report, with my 2nd test, things went much better.

1st off, my reloads. I was trying to use up some powder I was given, IMR-4198, rather fast rifle powder. I also used some 90 grain bullets. Reading elsewhere I saw mention of using a slower powder & heavier bullets.

I did another test batch with 100 grain bullets, and a upper loading of Ramshot TAC(30 grains)I think all 10 cycled fine, one failed to strip from the magazine, not a load issue. These rounds did not lock the bolt back on the last shot, the factory rounds did. Both ejected near the same distance, not real far, 4’+ a bit estimated.

I also used 2 other magazines, lubed them again before hand. The grouping was pretty good, casual testing. My lower should be broken in just fine, it’s part of a custom midweight setup I use for prairie dogging.

It still bugs me that the set screw in the gas block is so tight. I should be able to deal with that. I gave things a good cleaning and lube before I shot, but my next step with be another detailed internal cleaning and checkout.

Anyhow, on the upswing I think.

[FRB6.5]

Letting some Kroil or Liquid Wrench soak into the set screw threads for a few hours may help.

[wiguy]

I did put some Kroil over the set screw, still frozen in, not buggered up to much. My plan is to acquire a better tool/bit tomorrow.

The gas adjustment screw is out about 1 to 1.5 threads, backed out of the block. Of course the set screw has it locked in this position.

I took the bolt all apart, the bolt does seem rather stiff inside the bolt carrier. I cleaned everything and used a bit of slippery lube.

These rounds tested were the very 1st rounds for this upper, maybe 20-25 so far. My 2nd test went much better. Can I attribute some of this to ‘break in’? That may be more wishful thinking. Again it shot rather well, though I was mostly testing function. I have a 6.5-20 prairie dogging scope mounted.

My main goal is to free up the set screw. If that happens I will check where the gas screw is adjusted to, then more shooting.

[FRB6.5]

A silly possibility. Have you tried backing the gas screw out? It's possible it was assembled in the wrong order and the gas screw is acting as the locking screw for the set screw.

[wiguy]

Well, 1/2 there. The gas adjustment screw backed out normally, reasonable tightness. The set screw is still not wanting to come out. I’ll try a better fitting Allen tool today.

[NeilVT79]

I don't know where you guys got you're info on the PSA adjustable gas block but their is some misinformation in here.

The front screw, parallel with the barrel, is the set screw. The side screw, perpendicular to the barrel, is your gas adjustment screw.

Back off the front screw first, adjust the side screw, then tighten the front set screw.

[wiguy]

Thanks Neil. I have both screws loose and adjustable. Now I will go back to the drawing board with testing. I ‘assume’ if I was having cycling issues, and not locking back in last round(better now) I would want the ‘gas adjustment screw’ all the way in? ‘Full gassed’?

Just trying to get to coyote hunting reliability

[FRB6.5]

Unless there is more than one model of gas block, simply looking at where the set screw on the side of the block is in relation to the gas port shows which is which. Side screw on mine is well forward of the gas port.

PSA themselves have caused confusion on this as well. https://www.ar15.com/forums/AR-15/Adjust...18-732340/

[NeilVT79]

Thanks Neil. I have both screws loose and adjustable. Now I will go back to the drawing board with testing. I ‘assume’ if I was having cycling issues, and not locking back in last round(better now) I would want the ‘gas adjustment screw’ all the way in? ‘Full gassed’?

Just trying to get to coyote hunting reliability

No prob. Here's what I do:

With the gas adjustment screw all the way IN(clockwise) your bolt will not cycle, however, its a good place to start. Load one round in the magazine and fire, if the bolt does not lock back on the empty mag turn the adjustment screw OUT(counterclockwise) one full turn. Load one round in magazine and check if it locks back on the empty mag again. If not turn one more full turn and repeat until it locks back on an empty mag, then I like to turn it out a half turn and tighten the set screw. Run a few different loads to make sure it functions with all your ammo.
Hope this helps.

[wiguy]

Thanks, I will try that today, then report.

[NeilVT79]

Unless there is more than one model of gas block, simply looking at where the set screw on the side of the block is in relation to the gas port shows which is which. Side screw on mine is well forward of the gas port.

PSA themselves have caused confusion on this as well. https://www.ar15.com/forums/AR-15/Adjust...18-732340/

There may be different types, Im using the AGB that came with my PSA 12" upper. The side screw all the way in cuts off my gas completely.