Two possibilities:
1: (highly likely) He was shooting the wrong ammo in an 8mm Mauser.
2: (also possible) It was re-barreled in 30-06 when they cut the stock up.
Looks like an 'ol large ring 98, perhaps.
My money is on # 2. That was a pretty common occurance during the sporterixing craze. Wish they hadn't of done that! Lots of good Springfields,Krags,Mausers,etc. around like that, but sure hurts the collector and historic value, although they are perfectly useable guns.