Mauser headspace

[guntech]

The German's, WWII. Considered their rifles safe with up to 13 thou of headspace. reloads or case life was not a concern for them.
depending on how you installed the barrel to start with, and how tight it is on there. would be the starting point for me.

And they used steel gauges to set the correct headspace... military typically use 3 gauges, a go gauge, a no go gauge and a field gauge. The rifle is considered usable if the bolt closes on a go gauge or a no go gauge. If it closes on a field gauge it is supposed to be pulled out of service I believe...

Commercial rifles use a go gauge and a no go gauge to determine service.

This has nothing to do with a cartridge case head clearance on manufactured ammunition in a chamber.