Need some help with ar15 upper....

[Wallace's]

Works fine with 14.5" and 16". But its prefers when i run a heavier H2 buffer instead of the H1. Where as the 10.5" won't even cycle with H1 or H2, and runs...ish.. reliably with a carbine standard weight of 3.0 oz. with Lake City X193 5.56

Do you have a field gauge? With it being an el-cheapo barrel, the chamber could have been poorly finished and tight as well.

 

[Wallace's]

I fussed with a blackout pistol barrel with a carbine length gas/short dwell time system fer a while and never could get it running smooth.

Drilling can leave a burr

I would dump the barrel for a barrel with a pistol length gas system.

IMO 2” of dwell time ain’t never gonna run smooth.

BAD ADVICE

CRANE has a spec of .071 for 10.3-10.5" barrels and carbine gas (Literally done for the MK18 still being used today). Pistol gas is for 300BO, not 5.56 regardless if its an option. If properly gassed and assembled, 10.5" will function just fine.

 

[Wallace's]

Who made the barrel (and other components)?- Barrel Faxon Firearms, gas Block Midwest Industries, gas tube is generic, upper made by X-Products, Bolt/BCG ,ade by Aero Precision
How did you check gas block alignment? (95%+ this is the problem) -> is the barrel dimpled?
- Bottom of barrel is dimpled for gas block seating. Dimple aligns with gas port on top side of barrel, Removed set screw and check alignment. set front screw to make sure it did not rotate, and then set rear set screw into dimple. carbon build up on gas block and top of gas port show gasses are being directed into block. Rear screw should be set first to align the block with the dimple properly. Then you tighten the front(muzzle end). Red 272 loctite should be used for install as well on the set screws.
Verifying a gas key is sealing is very difficult unless it obviously loose.
-Sprayed WD40 into Gas Key, and blew air into key, looking for bubbles. Meh, not really going to show well. Did you verify the fasteners would not easily loosen (just takes light pressur with a hex key). Also, how does the staking look?
What size gas port? No, calipers will not suffice. You need a pin gauge set. (knowing who made the barrel would help possibly without needing a gauge pin set)
- Still need to do. This is an important variable.
What brand of XM193?
- Lake City
How did you verify the gas rings were ok?
- Gas ring tested (not scientific) by bringing bolt forward position from the BCG and standing the bolt face without the bolt collapsing back into the BCG. Did you visually inspect the rings? Picture? Does the bolt take abnormally firm effort to move or can you flick it outwards once in the collapsed position?

Thanks for your help!

Comments in red.

 

[Wallace's]

Comments everywhere!!!!!

Still confused somewhat though. This went from originally listed as a 11.5" upper issue, to a Faxon 10.5" barrel, to now a 10.5" AR Stoner...why such discrepancies in your thread?

 

[Plinker66]

BAD ADVICE

CRANE has a spec of .071 for 10.3-10.5" barrels and carbine gas (Literally done for the MK18 still being used today). Pistol gas is for 300BO, not 5.56 regardless if its an option. If properly gassed and assembled, 10.5" will function just fine.

Wallace thanks for chiming in with your expert opinion but please understand that I wasn’t sayin that a 10.5” barrel won’t run on a carbine length gas. That’s my 223 pistol setup and it works fine. See my post #23 above.

I was sayin that I think a 2” dwell time 223 pistol barrel won’t run right. That would be like running a 9” 223 barrel on a carbine length gas system.

I think we are in agreement Wallace; I was focusing in the 2” dwell time. The OP got us both turned around a bit by sayin that he had a 2” dwell time 223 pistol barrel.

Again, thanks for chiming in.

 

[Plinker66]

Maybe the OP just pushed the gas block up snug, when it needed a gap. Like I did on my first build or two. See post #3.

 

[Wallace's]

Maybe the OP just pushed the gas block up snug, when it needed a gap. Like I did on my first build or two. See post #3.

He also claimed the barrel is dimpled. If the barrel dimple was indexed off the gas port (which it should), this would be a non issue as it would self align and show if the gas block was machined with a provision for an end cap or not without having to measure anything.

 

[Wallace's]

Wallace thanks for chiming in with your expert opinion but please understand that I wasn’t sayin that a 10.5” barrel won’t run on a carbine length gas. That’s my 223 pistol setup and it works fine. See my post #23 above.

I was sayin that I think a 2” dwell time 223 pistol barrel won’t run right. That would be like running a 9” 223 barrel on a carbine length gas system.

I think we are in agreement Wallace; I was focusing in the 2” dwell time. The OP got us both turned around a bit by sayin that he had a 2” dwell time 223 pistol barrel.

Again, thanks for chiming in.

Ok, where was 2" dwell time mentioned? I am randomly not seeing comments here and there. so I literally might have missed something here..

 

[Plinker66]

Looks like The OP has taken his 2” dwell time post down. After I asked him whether he was measuring or estimating. How utterly confusing.

 

[Wallace's]

Looks like The OP has taken his 2” dwell time post down. After I asked him whether he was measuring or estimating. How utterly confusing.

Agreed. I am out on this thread until we get 1) GOOD pictures 2) consistency in reporting data/issue.

Just grasping at straws at this point.