[tobnpr]

^^^
Here's the thing...
If you have a chamber burr, or some sort of foreign matter in the chamber shoulder, it will prevent a case- or a go gauge, from seating fully on the datum- that's why you need to rule out that whatever is marking up your brass isn't preventing the round from seating before you check chamber depth/headspace.

At that point, it matters little whether you're using a properly FL sized case, or a hardened precision gauge- both should chamber. I've seen chambers scratched up by swarf that left ugly marks on the brass but didn't affect chambering, or extraction. If there's no raised burr(s) or debris preventing the rounds from seating, it IS a short chamber (or perhaps a different bolt given it's a used rifle). Either way the chamber would need to be deepened.