The cases may have different weights because of different wall thicknesses. Less/more room in the case will make a difference in pressure. For precision work it could make a difference in hits. Since my life is about miles, not inches, none of my work is precise. It wouldn't matter to me but if that's what you're after, I'd seperate them by weight once they are all trimmed to the same length. Find out for yourself if it makes a difference and buy, big lots, seperate, then trade off any that don't conform to the optimun weight for your rifle and buy another lot.