Re: New brass short
If they are all under max, one option is to shoot them, then size and trim. Once they are fireformed, you will be able to keep them at a consistent length.
If you trim first, I think they will vary by a few thousandths after the first firing.
If this is a hunting rifle, case length is probably moot. I haven't seen that varying case length affects hunting accuracy. If shooting F-class or other competition or your rifle shoots 1/4 min or less, then it may.
I, too, used to get more hung up on case length. Your chamber is probably much longer than Saami, anyway.
I now have chamber gauges to measure the length of MY chamber. then I trim .010 less than MY max length, which in some cases is still longer than SAAMI.