I have noticed that different manufactures have different measurements for brass. Nosler is noticeably longer headspace than others. I like a short chamber so there isn’t as big of swings in fired vs virgin. If the smith headspaced off a different brand of brass I could see having to bump the shoulders back a little. I recently had to do this with virgin brass just to get rid of the random few that were .001-.002 longer so they would all chamber easily.