Does this sound like a mis-aligned gas block?

[aaronk]

Gun is an 18" .308 with rifle length gas system running a Superlative gas block with a JP Enterprises full mass bolt carrier and H2 silent capture buffer. Gas port size in the barrel was slightly over sized with the intention of running an adjustable gas block.

Unsuppressed: With gas block adjusted for maximum gas the ejection is perfect at 3-4 o'clock but magazine will not lock back. Gun will have cycling issues if not firmly planted in shoulder. Obviously can't give it any more gas as it's already maxed out.

Suppressed: Starting with gas block adjusted for maximum gas pressure the gun is obviously over gassed. Using the bleed off feature of the Superlative, it seems like the gun still can't bleed off enough excessive gas to get the ejection in the 3 o'clock range so the gun is still over gassed.

Give the bolt/buffer/gas length is fairly standard for an AR10 I'm leaning towards gas block alignment? My train of thought is as follows... If the gas block is slightly mis-aligned I'm not able to get all the gas I could potentially utilize when the gun is unsuppressed, but it's enough to still allow it to cycle and eject. This would also mean that I wouldn't be able to necessarily bleed off the full volume of gas when I'm running suppressed which is why even with large bleed off adjustments there's still too much gas.

Does this sound like a gas block alignment issue or is there anything else I could do to narrow in on what's going on? Planning to pull the gas block and double check alignment when I get home tonight.

 

[nn8734]

Does the gas block look canted to one side?
Is the gas block a set screw type or clamp type?

Is there any tension on the gas tube?

What buffer spring? Maybe too stiff...

What ammo? Factory or hand load? Different types/manufacturers?

Most gas blocks have ports larger than the port on the barrel to allow for some alignment margin of error.

I would check alignment first and maybe R/R the gas block to be sure and try shooting it again and see if the symptoms persist

 

[aaronk]

Does the gas block look canted to one side?
Is the gas block a set screw type or clamp type?

Is there any tension on the gas tube?

What buffer spring? Maybe too stiff...

What ammo? Factory or hand load? Different types/manufacturers?

Most gas blocks have ports larger than the port on the barrel to allow for some alignment margin of error.

I would check alignment first and maybe R/R the gas block to be sure and try shooting it again and see if the symptoms persist

Gas block looks visually aligned.

Set screw gas block with a dimpled barrel. I did set the gas block .025" off the shoulder as the directions state and it felt like the screw hit home in the dimple. Now that I'm typing this out though, maybe I'll try the gas block all the way against the shoulder and see what happens.

Gas tube feels normal.

Buffer spring I'll have to check, but it's the stock spring that comes on the H2 silent capture assembly.

Factory 175g Federal Gold Medal Match is the only thing I've run.

Thanks!

 

[nn8734]

If the fasteners located the barrel's dimples and there's no tension on the gas tube, its prob installed correctly. However, it may be worth pulling off just to check for obstructions, debris and confirm correct alignment on re-installation. Also, perhaps blow some compressed air through the gas tube while you're at it.

Afterwards take it out to the shooting spot and re-test first without the can to see if it will cycle normally. You can try first by locking the bolt back, loading one round in the mag, installing the mag then chamber the round by releasing the bolt catch. Fire the round and see if the bolt carrier group will lock back on its own on the empty mag. If if fails to lock back, something else is wrong (spring, buffer, gas system issues, bad gas block, etc....Meanwhile, make note of where that case ejected and any pressure signs on the case.

If it does lock back and the case looks fine, load 5-10 rounds and slow-fire, observing ejecting the pattern as you go.

Then repeat but with the can installed, making appropriate adjustments on the gas block as required.

Hopefully you wont have any further issues.

 

[hlee]

Go to JPs site and buy the steel weights for your SCS. Replace the tungsten weights in your SCS with the steel.

The Superlative gas block can be run as a bleed of system or a restriction system. Set it up to restrict the gas for suppressed. Open it until it locks back on empty. Open it a click or 2 more...

You likely won't get optimum function for both suppressed and non-suppressed at one setting.

Don't sweat ejection angle too much.

 

[aaronk]

Forgot a buddy has a borescope! Anyways, gas block looks aligned well enough, maybe just a smidge off, but certainly not enough to affect anything I wouldn't think.

Gonna play with the buffer weight next. Now I remember why I told myself I'd never mess with building an AR10