Joshua, Here is something interesting. I mic'ed 3 barrels, .310... .312 at the lands. I took out a .311 bullet and a .323 bullet. Neither would go into the bore, at all. I measured 2 24/47's and a Czech '98. Get some Remington 170gr ammo to try her out. Loaded to .30-30 spec. You should get a good idea.
Freedom is not free. The best of us always leave too soon.
With the 'S' stamp,it 'should' be okay with modern USA-made 8X57 ammo - our factory ammo is loaded a good deal less powerfiully than the original European8X57 ammo.
But to be on the safe side, you need to get yourself a Mauser and use it as a shooter, and keep the old Commission Rifle as a collector piece. The old Gewehr 88 rifles often go for a few hundred bucks to someone who knows what they are. Yeah, you stole it, you lucky dog!