I have a 16” A1 upper on a KP15 lower with the captured buffer spring. I put somewhere near 300 rounds of steel case through it with no real problems, maybe one or two failures early on when the action was a little rough and chunky, but now it feels very smooth.
Yesterday I did a function test with some IMI 77, which was the first brass cased ammo that I’ve tried. I only have a few boxes of this, so I shot four rounds and had no problems. Once I pulled the magazine and tried to eject a round, though, the unfired cartridge stayed in the chamber. I worked the action and again had the same result. On the third try it ejected. I then worked the action through the rest of the magazine. Seven of the remaining rounds either stayed in the chamber on the first try, had a very weak ejection where the cartridge was pulled to the rear but not flung out of the action, or both.
I should go fire this mag to see if the problem happens when it’s cycling for real, but I don’t see why it wouldn’t, and I thought I’d ask what to look for before I go wasting the brass ammo.
What could be wrong and how should I proceed?