Originally Posted by INSIDIOUS

Sort them by brand. Clean them. Deprime and size the primer pocket, neck size and trim to length. (assuming all fired in the same gun, otherwise you need to hit the shoulder also) Weigh them (magic marker on each) and chart that data on a histogram. From there pick your like groups. Once you have that, the exteriors are all the same the interior volumes should be the same and hence consistent pressures.