The used casings stovepiping suggests the possibility of a bad ejector, weak ammo, a dirty action, too stiff a main spring, or limp wristing. Basically the toggle isn't going back hard enough to pitch the case free of the chamber area.
Your mag catch could be worn, or the slot on the mag. could be worn or in the wrong spot. Sometimes you need to experiment to find the right mag. that works with the right gun. And the right ammo, etc. Nothing is simple with these but that's part of the fun.
Dito the feeding issue. Try other ammo, consider the main spring, etc. Something as trivial as the bullet shape can dramatically effect the function of these guns.
Now get back to the range...
dju
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