On a couple of my rifles I normally only get one firing before my primer pockets will no longer hold a primer. Sometimes upon extraction, the primer will fall down into the action and I will have to shake the rifle around to get it out before I can shoot again.
When I was talking with Lake City Arsenal about some match ammo issues some years ago, the engineer said their proof loads typically loosen primer pockets a bit, but never had any primers fall out after firing them in pressure test barrels. New primers seated in fired proof load cases went in somewhat easier.
I've shot those same proof loads Lake City Arsenal uses in M1 Garands, then reloaded the same case with proof load components 2 or 3 times before the primer pocket was too loose.
Arsenal 7.62 NATO proof loads have 65,000 CUP or 80,000 PSI. Service loads have 50,000 CUP or 58,000 PSI. Which more or less tells me that folks loading ammo such that primers fall out of new cases are... ....well, readers can plug in their own descriptive term. We each decide what our margin of safety is.