Ditto on checking for over-waxed ammo. I mistakenly tried to use a bunch of bulk CCI ammo in it, and the wax f--ked things up pretty good. The last 3 times I've been shooting with it I loaded the magazine up with Stingers, since they seem to have no wax on them - I can do 3 mag dumps in a row with maybe one jam. Clean the drum of any wax buildup, and load it full of stingers to verify that the mag works well, then start branching out into other ammo. In large cap 22 mags I make it a point to try and stick to copper round nose and not funky huge hollowpoint or truncated cone ammo. I know stingers aren't cheap, but when I use them in the GSG 110 rd drum mag, it's among the most reliable magazines I got.