I once read a good write up on how to fit your cases perfectly to your chamber. However, I use a "Lee" case trimmer, which trims the case to SAMMI "minimum" length. I guess .010" shorter than "maximum" length. This trimmer provides excellent consistency on the short end and seems to be the easiest and quickest way to get there. My BIL wants to sell me a Redding case trimming set for a good price, but I don't know that I would ever use it? Good Luck ! :) ... Jim