Probably shrunk on first firing as the shoulder filled out. That's normal for never-fired, but yours seem to be a little shorter than "normal."
Not really a big deal. Usually, I don't do much case prep with virgin brass except with a nail set for dinged necks, and a really light hit with a die grinder burr (not in the grinder) to chamfer just a little.
After the first firing of the lot, I'll measure a good sample and try to find the "shortest" length, and use that as a basis so all the cases are the same when I'm done. I set a trimmer up for a couple thou longer, start banging away. Then I set the burr up in a drill press with a stop. Anything that doesn't bite on the burr gets culled.
