Mine was an IAB and it never locked up on me. It held 110 grains of loose powder with the bullet shown above. I used 100 grains a few times. The only problem with using that much powder was excessive flash out of the receiver. it was hella accurate with it tho. It's funny, 80 grains was very accurate, 90 grains was all over the place, 100 was better than 80.