I built a AR for hunting season a month or so back. 20", rifle length gas system, I used a carbine length mil-spec buffer tube/spring/buffer. Assembled it all, put a magazine in with a single round, it shot fine, kicked it out, bolt locked back. Repeated this a few times, same result seemed fine. I then swapped out to loaded mag, same thing, fire, shot, extracted fine, chambered the next round, shot it, extracted, repeat 20 something more time, bolt locks back. It seems fine. So I tape off everything needed to be, give it the desired rattlecan look I wanted.

The rifles sat up after paint a month or so now, broke it out today to get it sighted in. Chambered the first round, shot, no extraction. I dropped the mag, cleared the chamber. Reseated the mag, chambered the round, shot, extracted but didn't chamber the following round and left a scratch down the top and a slight dent at the shoulder. Continued to do this regardless of what ammos or magazines I used. Switched to a single round in the mag, it seems to be shortstroking, wasn't locking back on the mag.

What could cause this a month or so later after the rifle operated fine? Im not feeling any gas around the block while shooting. Any suggestions would be great.

using same ammo?



Bruce

Well, you painted it, and let it sit.  Tried cleaning the chamber? relubing? checking for bleed-over from the painting inside the upper?

Yessir




Cleaned and re-lubed everything, I went over everything pretty good to make sure no bleeding would happen, Ive gone over it again this evening after tearing it down and theres no visible anywhere.

Check the bolt carrier for loose screws.

 

Yup yup, one of the first things I checked, I figured it was the gas key. Everything was tight though.



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Update: Broke it down, cleaned and lubed everything up again. Got it to cycle properly, one round in the mag, she locks back everytime. Did it 10-15 times without issue, which I interpreted to mean its cycling properly, gas system is fine, which was honestly my biggest worry. After loading mags with more than one round, chambers the first fine but the second is jamming it, the second round doesn't seem to be getting the light scratch down the casing just a larger dent in the shoulder now. It seems to me like a magazine seating issue but its recurring in any and every mag I have, ASC, Okay, Colt (20s and 30s), Magpul.