Could also be the ammo. The "brass" heats when you fire and if it doesn't cool quickly enough, or is a tad oversize, you may have a problem ejecting.
Try test firing it, and next time it jams, wait a minute then try pumpimg again. If it works then, try another brand of ammo.
I had problems with Kent a few years ago, but solved that in a hurry: no more Kent!
(I don't shoot steel, so that was either bismuth or tungsten, don't recall).
SAFETY FIRST: RELAX!!!
There's lots of birds, and you don't want to have to explain to your buddiy's wife that you just made her a widow.
Control the muzzle, and check the safety.
Your life depends on it, and so do your buddies'