[Unclenick]

Interesting problem. I don't recall what press you're using. How rigid is it? Do you have your lock rings good and snug? The reason Redding makes those competition shell holders in different thickness is to give a hard stop for the die, so you can apply some excess pressure to be sure you force the same fit each time. That way a case that goes into the die harder than another doesn't change the sizing length by causing a different amount of press stretch or thread compression than another.