I just changed powders from 700X IMR (4.2 grains) to bullseye (3.8 grains). I'm using plated bullets, so I've been having very low charges. I loaded about 300 rounds and I noticed several rounds (probably 5-10%) of the bullets fell back in the case. Is it my sizing die? Too much on the expander die? Seating die? I usually don't crimp them at all, but I ran these bullets and put a mild crimp, but it didn't seem to solve the problem.