Shorty cycling issues

Throttle_monkey1

Throttle_monkey1

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Hey guys I pieced together an AR and it has an LMT 10.5" upper, and it won't cycle. When I fire a round, it ejects the spent casing but won't pick up another. I'm pretty sure it's the buffer. What buffer should I be running in this thing? A heavier or lighter one?

ETA- I tried reminton 55 gr fmj, m193, hornady steel cased training ammo 75 gr bthp and 75 grain T2 TAP. None of them worked.
 
Done that. It's just not cycling far enough back to strip a new round. Or maybe it's going so fast it's going faster than the mag spring can push up the next round.
 
A heavier carbine buffer to slow down the action is beneficial with short barreled ARs. A heavier carrier also helps in that regard.

Check your gas key is tight, obstructions in the gas system/tube, make sure you can cycle the action and pick up a round manually and that the bolt will lock back on an empty magazine.

Make sure you don't have a rifle action spring installed in a carbine stock.

Start there.
 
I'm pretty sure it's the buffer weight. I will try buying a lighter and heavier buffer and go from there. I've also read that these LMt uppers are spec'd to run with the CAR buffer. Thanks guys!
 
Throttle_monkey1 said:
Done that. It's just not cycling far enough back to strip a new round. Or maybe it's going so fast it's going faster than the mag spring can push up the next round.
Click to expand...

That won't be an isssue with 5 round mags as the weight of the ammo is so little to move.

Will it lock back when fired with an empty mag? If so is it catching on the bolt or the bolt carrier?
 
In general, a lighter buffer will allow the gun to cycle with more force. In a shorty using a CAR gas system, a standard or H buffer should be fine. If you use a pistol gas system (think 7.5" barrels) you need a H2 or 9mm buffer to moderate the exaggerated gas pressures and increase lock time.
 
It won't lock back on the last shot. I'll try replacing the gas rings, but i still think it's the buffer. It has a short buffer, but I have no idea what type. I took the handguards off and the gas tube has a little bit of play, a very minute amount. But I've never felt an AR gas tube before so I don't know what to expect.

I will contact the guy I bought the lower from and see what buffer he built it with.
 
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