I've searched and found several symptoms of bolts not locking back, but none seem to apply. I probably have only 250 rounds of 223/5.56 through my AR, and probably 1200 through my CMMG 22 conversion kit (I'd shoot some 223 through it after the kit to keep the gas tube clean.) Here's what's happening...
Yesterday I was shooting American Eagle 223, and the first magazine locked back ok. From then on, nothing would lock back... I thought maybe the magazine had a weak spring or bad follower, but none of the other magazines would lock back either. I thought maybe it was weak ammo, so I tried some Winchester 5.56 (which I've never had an issue with) and it wouldn't lock back either. Whenever I'd pull the charging handle back on an empty magazine, it would lock back.
This made me think maybe it was a gas issue, so I cleaned the gas tube the best I could in case it was short stroking. I took it out today and still had issues. If I manually pushed the bolt catch up when shooting, that would lock it back (so it wasn't the bolt catch, and it wasn't short stroking). I tried a friend's magazine, and a couple others of mine (all are pretty new PMAGS), and none fixed the problem. I then put my upper on his lower (to make sure it wasn't my bolt catch), and it still wouldn't lock back. However, I noticed if I put a little upward pressure on the magazine, that would seem to engage the bolt catch enough to lock it back on an empty magazine.
Does anyone have any idea what is happening here and why? I've done as much troubleshooting as I know how, but I'm at a loss. Your help is appreciated!


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