What is TIR? Also, is it required that you use "small base" dies for AR reloads?
Total Indicator Runout.
No.
Anything to the right of the 100ths place in overall length is irrelevant.
Yes sir. Total indicatior reading, but for run-out. I like straight ammo. It tends to shoot better than crooked chidt. Im running small base dies for my CLE chambers. Get good accuracy and good enough longevity out of my brass. Not that im too concerned about it. Brass is free around here.
If adding crimp reduces your indicated runout, you probably have something funky going on elsewhere in the loading process. Obviously we all like straight ammo for accuracy, but crimping isn't usually necessary or helpful.
