This could be a variety of things and unfortunately you are not there to get
a first hand look. What does it mean that the cartridge comes out at an angle and
the bolt stops? That the cartridge jumps free and is at enough of an angle that it
is jammed sideways against the face of the bolt kind of like a stove pipe jam?
It could be-
The feed lips of the magazine are ever so slightly nicked or dented
causing friction. The more rounds in the mag the greater the spring force the
greater the friction. When there are fewer rounds in the mag, less friction and
the gun works.
The mags could be loose in an up/down direction. Use duct or masking tape
to tape the mag tight up against the receiver. If this fixes the problem it's the mag.
The shooter could be slowly squeeezing the trigger causing the sear to drag
on the bottom of the bolt slowing down the bolt, as opposed to decisively pulling
the trigger and dropping the sear all the way.
If it's more than the top round in the mag the gun may be short recoiling. The
bolt recoils far enough to eject the case but not far enough to pick up the rim of the
next round and the front
end of the bolt scrapes against the side of the next round pushing it out of the mag
where it jumps free of the feed lips and jams the bolt.
Short recoil could be the ammo, the trigger pull, or a shot out barrel.
To check for proper power fire the gun on semi and the bolt should
lock to the rear on the rear sear notch every time. If not the gun is short
recoiling due to not enough power.
Edited by reconbob, 14 February 2020 - 12:13 AM.