I'm still new to the rifle side of reloading and have spoken with a number of folks who skip the crimping station on 223 in most cases, FMJ's not withstanding. In my first session out testing workup loads, my semi-auto shoved the bullet back into the case twice out of about 20 rounds. I had set bullet depth specific to the chamber, although I did go as long as possible. I've had bullet pushback with low end factory rounds that had bad crimps in this same rifle. I skipped the crimps on these rounds based on feedback from others. Hornady Vmax 40 grain, 25.7 grains CFE 223. Dillion dies.