I'm asking about the bazillions of surplus Mauser rifles that were imported after World
War II. These rifles' barrels were probably not chrome plated or otherwise given a protective finish or treatment on rifle bores.

What range of amount of factory ammunition and hunting reloads would these rifle owners expect "hunting" accuracy (4 MOA). Let's anticipate the owner takes care of rifle - cleans, lubricates, has improved sighting system, etc.

No Mauser barrels were chrome plated. Here is what they would do when new. From the DWM catalo0g, 1904;
7MM; 4.7 inches at 219 yards.
7.65mm: 5.1 inches at 219 yards.
7.9mm: 7.9 inches at 219 yards.
Somewhere I have a picture of girls at the Mauser factory testing a Kar98K with a machine; can't find it now.
You will have to shoot yours and see how accurate it will be.

Springfield 03 and 03A3 barrel life is somewhere in the neighborhood of 5000 rds (+/-). I'd guess a military Mauser barrel would be close to the same.

https://bulletin.accurateshoot...=barrel+life+program