Never mind the bump firing. I've tested lots of mags by loading drill rounds(that are reliable) and then hand cycling. You don't have to beat your hands up, just pull the actin all the way back and let go. Repeat. Just the same way as putting on a fresh mag. You can use the little hold open but...why? If you've loaded the mag correctly, the drill rounds are OK, and you don't ride the op handle forward, it should work.