AR jamming problem

[RK808]

My friend's AR has been short stroking with all kinds of ammo after about 60-80 rounds. We've cleaned it before shooting, tried swapping out the gas block and the gas tube. It's not his buffer tube assembly, we've tried swapping uppers, lowers, and bolt carrier groups. It'll fail to cycle the next round either by jamming on the round or closing without picking one up. Any ideas?

[twolane]

You've mentioned most everything else... did you try swapping mags?

[tanakasan]

Clogged gas tube/misaligned gas block?

Robert

[Synergy]

Clogged gas tube/misaligned gas block?

Robert

I was thinking clogged gas tube, Spray it with some brake kleen.

[MT1]

You've mentioned most everything else... did you try swapping mags?

That would be my suggestion, many function issues can be traced back to the mag.

[RK808]

I was thinking clogged gas tube, Spray it with some brake kleen.

We thought that was the problem so we bought a new gas tube. Wasn't it. Used various magazines as well (PMAG, USGI, USGI w/ Magpul followers).

[bohoki]

yea that sounds like a slow feeding magazine

what is your magazine type currently?

polymer, aluminum, steel

[croc4]

buffer spring?

Maybe a rifle length instead of a carbine length?


croc4

[tuna quesadilla]

You said "All kinds of ammo" but what exactly do you mean? Tell us what kind of ammo you're shooting...

What kind of rifle is it?

Gas system configuration?

Built or bought?

We can't help you without details.

You said you've swapped uppers AND lowers? So, you've basically put together brand new rifle configurations and you still had the issue...? Something isn't adding up here.

[MT1]

You said you've swapped uppers AND lowers? So, you've basically put together brand new rifle configurations and you still had the issue...? Something isn't adding up here.

Yeah, once you answered the mag question, that means you've built completely new rifles and the problem persists....

[CIV Tactical]

put one round in the mag and fire. If the bolt doesnt lock back your most likely undergassed. Check your gas key for tightness and test your gas rings by taking out your bcg and put the bolt in the in battery position and hold just the bolt with the carrier facing down. If the carrier falls and uncams the bolt you need new gas rings. If thats all good then you need to check for proper gas block alignment. If thats not it you most likely need to open up your gas port. Carbine length gas port should be .060-.064 thousands and rifle length gas port should be .090-.094 thousandths and midlength somewhere inbetween.

[Dragon]

put one round in the mag and fire. If the bolt doesnt lock back your most likely undergassed. Check your gas key for tightness and test your gas rings by taking out your bcg and put the bolt in the in battery position and hold just the bolt with the carrier facing down. If the carrier falls and uncams the bolt you need new gas rings. If thats all good then you need to check for proper gas block alignment. If thats not it you most likely need to open up your gas port. Carbine length gas port should be .060-.064 thousands and rifle length gas port should be .090-.094 thousandths and midlength somewhere inbetween.

Sorry, but im not a believer in the hold the bolt and if the carrier falls u need new rings. Maybe it works if u have low gas pressure coming from the barrel to the tube.

Mine fall ,and i have no issues.I carry extra rings just in case they fail Maybe im just lucky!?!?

[wash]

Well if the ring gaps line up, that might leak too much.

But how do you know the buffer tube assembly is OK?

Assumptions can cause a lot of problems.

[HighLander51]

My friend's AR has been short stroking with all kinds of ammo after about 60-80 rounds. We've cleaned it before shooting, tried swapping out the gas block and the gas tube. It's not his buffer tube assembly, we've tried swapping uppers, lowers, and bolt carrier groups. It'll fail to cycle the next round either by jamming on the round or closing without picking one up. Any ideas?

Did you buy it, or build it? You say it runs for 60 to 80 rounds, that's not the ammo, or the gas block, or tube, or recoil spring, or magazines. What kind of ammo are you using?

[Munny$hot]

where is the ejection patteren 1:00/3:00/5:00 ?