To keep it fair all brass was uniformly trimmed, and seating and crimping were done in seperate steps.
I shoot mine from a very heavy bolt action, with hot loads it barely moves when fired. I am not worried about rounds backing out. Neck tension in all of my rounds is quite suficient. I have loaded for several friend's AR platform rifles. Ronds that chambered with full force were extracted and measured to see if the bullets pulled out any from slamming to a stop in the chamber. None of the bullets backed out, or were pushed in.
Though if you get better groups crimping your rounds then by all means crimp them. Go with what works best in your gun.
No matter how many times you do it and nothing happens it only takes something going wrong one time to kill you.