Recently acquired a .375 Cheytac with Peterson brass/dies. These brass have been re-loaded prior 2-3 times. Max case length is 3.028. I haven't annealed or re-sized these yet, but most are undersized in the area of 3.020-3.024. Is this an issue?
Since SAAMI doesn't have an approved set of case/chamber dimensions you need to look at the C.I.P. dimension drawing which are all in metric (mm) then convert to English inches. Yes, it's a nuisance!
CIP lists the Max chamber length dimension as 3.040" when converted. So the trim measurements of your brass fall right into the proper length.
Remember, your brass length needs to be under the MAX sizes because the neck length in the chamber ends in a 45 degree transition angle. If your brass is too long, the neck will be crushed into the transition angle which raises your pressure significantly.