runswithelk,
In your first post, you said it wouldn't close on a 7x57 case. Contrary to popular belief, the 7x57 is not simply a necked down 8x57. As in Axel's comments, posted by Raimey above, the 8x57 is based on the M88 case. The 7x57 case is known as the M93 case, which has a head diameter larger than the M88 case(nominal .468"vs .473").Rim diameters and thickness are also different between the two. The bore diameter of 7.7mm is pretty tight, but is often seen in commercial barrels. If when you slug the bore, you find a groove diameter smaller than .318", I wouldn't be overly surprised. The chamber neck would have been cut large enough for a .318" bullet( maybe larger)and will be perfectly safe with commercially available 8x57IR ammo, such as S&B. Enjoy your very fine gun, it will give many years of good service.
Mike
