The German military changed the bullet diameter of 8mm bullets from .318 to .323 in the 1930's. It would be unsafe to shoot any Pre-WWII war era German made rifle or any rifle made into the 1970's in Eastern Europe with current production 8x57IS ammunition without first slugging the bore to figure out if it was a J-Bore of .318 or a I-Bore of .323. The designation for the pre-war cartridge is 8x57JS.

Ronald, yes. This is a typical German hunting rifle for the cartridge with the CIP name 8 x 57 I (this name did not yet exist at the time as far as I know). If you look for ammo, look for 8 x 57 I (without an S).
The 8 x 57 I is a strictly civilian cartridge. The bore diameter is 7.8 mm compared to 7.9 mm of the military cartridge and the maximum bullet diameter is 8.09 mm compared to 8.22 mm for military bullets.