AR Questions with .22 ARC Conversion

[foxhunter]

i have an ar with a Faxon 16" gunner match barrel, it has a rifle length gas system. i have a 6mm arc as well and it functions just fine , i took the lower off the 6mm and put it on the 22. it has a carbine length tube with collapsable stock. the rifle is a single shot, eject the spent shell but does not pick up the next shell. i pulled the buffer weight and spring, it has a red springco extra heavy duty spring and a h1 weight. i have another lower with an a2 stock and the 22 arc runs just fine on it, it has a rifle buffer weight. (6")

any suggestions? thinking of replacing the red spring with a aero mill spec to see if it will run.

 

[Walt Krafft]

Mixing lowers for different cartridges can be a problem. What cartridge is your problem upper chambered in and what ammo are you shooting? White Oak has a trouble shooting write up on short stroking.

 

[Sandstorm]

Put a stock spring in it and a standard buffer and give it a go.

 

[R.Morehouse]

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[Richard Jones]

I'm assuming non-adjustable gas block?

 

[Texas Solo]

I had same issue with with 300BO build. I had plenty of pressure, spent rounds flew 10ft. But it would not pick up the next rd. It was a Colt lower with H buffer. I swapped to a std carbine buffer and it's now 100% reliable.
Lose the H buffer before you try anything else.

 

[jelenko]

What gas system length is used on the 22arc upper?

 

[Oso]

When the bolt is cycling, but not picking up the next round it is either:
(1) the bolt isn't cycling far enough back to eject spent case and then pick up the next round
(2) the bolt is cycling too fast and slingshot forward skipping right over the top of the magazine.


# 1 is usually the result of not enough gas (misaligned gas block, gas port hole too small, adjustable gas block closed to far) or issues with cases sticking to chamber

#2 is result of too much gas &/or too weak of a buffer system. You see this a lot in 300BO with its pistol length gas port, which is needed to collect enough gas when shooting subsonic ammo. However, it becomes excessive amount of gas when shooting supersonic ammo. The gun requires either an adjustable gas block or a heavier buffer system (buffer weight and buffer spring) to slow down the BCG.

Grendel-based cartridges are upper limit of powder volume in an AR15, which translates to increased gas volume. You will need too either use an adjustable gas block or increase your buffer system. If you are running a Rifle length gas system then simply start with swapping out the spring and this will may be all that you need.

A couple of recommendations to resolve your issue and make your gun cycle reliably and smooth out recoil impulse.
Superlative Arms: Adj. Gas Block ($90 and one of best out there)
https://www.brownells.com/gun-parts...em-parts/ar-15-clamp-on-adjustable-gas-block/ (Clamp on Style)
https://www.brownells.com/gun-parts...ystem-parts/ar-15-solid-adjustable-gas-block/ (Set Screw style)

Wolff: Extra Power Buffer Spring ($18)
https://www.brownells.com/gun-parts/rifle-parts/rifle-recoil-parts/ar-15m16-xp-recoil-springs/