Not all Mauser or 8mm. are the same !
Uncle Mike stated it pretty good !
For most of the 8x57 Mauser ammo, except for the;
Steyr 1895 Stutzen Carbine, it's an 8x56R, and has a larger bullet, then a .318, or .323 dia., the Bulgarian 8x56R for the carbine is .329"/ 8.36mm. dia.
The .323" is...