I have to agree with AJ Peacock, the most important thing is that your brass isn't too long for your chamber, a few 'thou' over or under the 'trim to length' will make absolutely no difference to how your rifle shoots, as long as they're all the SAME and SQUARE, with a slight chamfer
inside and out.
When I start with new brass, I run them all through my neck sizing die to insure they are round, measure them all, find the shortest one in the batch, skim trim it to make it square and trim the rest to that length, chamfer and deburr the flash holes.
To get your trimmer set each time, you need to have a 'trim to length' case set aside as a 'set stop' to go into the trimmer each time.
I also have 'dummy' rounds set up for my bullet seating dies, with each different bullet style I might use in that cartridge, a 'dummy' round contains no powder or primer, just the projectile seated to the OAL that you have set for your gun/load combo.