According to my Collector Grade mauser book, the 8x60 was made with a .318 bore but loaded with .323 bullets.
Very deep grooves much like the rerifled military 98s that were .318 and rifling deepened to allow shooting .323 ammo.
https://www.amazon.com/Mauser-Original-Oberndorf-Sporting-Rifles/dp/0889352305
