AR-15 not cycling....

[sbryson21]

I made a trade for an AR from a member on here about a year ago. He built the rifle and everything was brand new and a really nice set up. I had put maybe a total of a couple hundred rounds through it during maybe 3 or 4 different times of shooting sessions, sighting it in and what not. Never had a failure to cycle or any problems. Well I took it out a few months ago and it turned into a single shot rifle. Pull the trigger, bang, and then would have to manually cycle the next round. I've cleaned it, tried the 2 different ammo brands I have, and shot with my PMags and steel mags but it won't cycle correctly with any of it. Just wanting to hear some ideas of what might be wrong (maybe need a different bolt?). Any ideas welcome to get my rifle up and going again, thanks!

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[eldbillbo]

clamp on, set screw or taper pin gas block (front sight base) ?

Gas tube have a roll pin installed?

are your gas key screws tight and properly staked ?

It sounds like a gas problem. somewhere there is a leak or if you have a set pin or clamp on sight base/ gas block it has shifted. or someone forgot to install a roll pin or it fell out of the gas tube . or the gas key has come loose. somewhere there is a gas leak.

other possibilities but unlikely are misaligned gas tube or key, use of early laquer coated wolf ammo, plugged gas tube or block .

 

[sbryson21]

I did have to tighten my gas block about a month ago after I noticed my handguard was coming loose. The gas block need to be slid back down and re-tightend. So maybe that was the issue? Also my AR has JP yellow springs and I just read that the lighter springs can sometimes cause failures with military grade ammo? (which I always run 5.56 through my rifle)

 

[sbryson21]

Also my gas block is set screw, so what is the best way to go about making sure it's set back on there right where it should be?

 

[Swedish K]

first off you say it fires but doesn't cycle so the yellow JP trigger group springs are not the issue.
I was going to say check the gas rings on your bolt but from the sounds of it the gas block has shifted so the gas port from the barrel is not lining up with the hole in the gas block this could have been a result of tightening it with the incorrect alignment or from it shifting after being installed.

 

[iamme]

You slid the GB back and retightened, I'm guessing slid it all the way to the shoulder which most GB aren't set for. there should be a small gap there where the handguard retainer would normally reside. I'm gonna guess the GasBlock isn't quite lined up right.

 

[blitz]

another vote for the gas block, i would pull the block and gas tube off and run a pipe cleaner though the gas block, gas tube and the gas port on the barrel.
if it is a set screw it should go right back into place, if it is a clamp on make some reference marks.

i am kinda a newbie to black rifles, only built a couple but this is where i would start.
could be that if it is a set screw type and it got a little loose it might have wore out the hole on the barrel where the set screw locks in so i would check this as well.

hope you get it running right.

 

[eldbillbo]

Also my gas block is set screw, so what is the best way to go about making sure it's set back on there right where it should be?

What i personally do and others may do something else with the set screw type gas blocks is when i install them i tighten the heck out of them then if it runs right i remove it look for the witness marks and either dremmel or drill indents in those spots got to be careful and exact cause if those indents are off you block will be off. so when i reinstall the set screws go into the indents then test fire again if its still good i then remove 1 screw and re install it with lock tight then do the other but 1 at a time so it does not loose its position

but if your block came loose then i bet thats the problem its off just enough where its not getting enough gas to cycle the bcg.

The JP springs would only cause ignition problems so there are not the problem. i own some of those and have never had a issue with them

 

[sbryson21]

Wow facepalm on the springs question, that was an obvious duh . But listened to your guys troubleshooting tips and took my rifle out today to check it. Cycled all 10 rounds as fast as I could pull the trigger, thanks for the help!

 

[madcratebuilder]

I did have to tighten my gas block about a month ago after I noticed my handguard was coming loose. The gas block need to be slid back down and re-tightend. So maybe that was the issue? Also my AR has JP yellow springs and I just read that the lighter springs can sometimes cause failures with military grade ammo? (which I always run 5.56 through my rifle)

There's your problem. The gas block is not aligned with the gas port on the barrel.

The gas port in the block is larger than the barrel port so you have some room for error, but not a lot, .010-.015 every one is slightly different.

 

[djgaloot]

I realize the GB was your issue but just for completeness in case others are troubleshooting, I had the same issue with mine. After carefully checking all of the GB alignment, etc. it still would not cycle. I replaced the gas rings on the bolt and the problem went away.