I have recently started reloading for my AR. I've got some 77 gr SMKs(cannelured) that I would like to work into a good service rifle match load that I will use out to 600 meters. I'm using once fired military brass that I picked up on the cheap. Accuracy to date has been decent, but I have noticed that bullets seated in the bottom of a mag, after firing about 8 or 9 rounds out of the mag, will measure a few thou deeper then what I seated them at. Recoil setting the rounds back is my best guess, and I figure crimping or increasing neck tension are two possible solutions. I've read extensively on the controversy of to crimp, or not to crimp, and have decided I will give it a try and see for myself. Not actually having used the crimp ring in my RCBS seater die, I'm probably going to pick up the redding taper crimp die, but not until I'm sold on it being something I'll actually use. Long question short, how much crimp do people put on their necks? Are we talking a few thou, .01", .05". Is there a sweet spot? Thanks gents, looking forward to the responses.