I always drool when I look at double rifles. I almost bought a Holland and Holland 450-500 BPE at a collectors show in Dallas last year. It was a gorgeous hammer gun, but that cartridge wouldn’t be fun for the smaller animals we have in Montana.
So what is the 8X57R? I’m assuming it is the German 8mm Mauser, with a rim. Mine was a 7X57R which is the same as the 7X57 with a rim…
It's JR, and that's the older .318 diameter bore, although most of the JR guns have .320-.321 bores in fact. The modern 8 Mauser rimmed is the 8X57JRS, a hotter load than the JR and with the .323 bullet. JB got my JRS drilling a while back. I believe he uses it for grouse hunting in grizzly country.
BF, the dohickey in the edge of the rifle extractor was not uncommon between the wars, when correct ammo was hard to come by after WWI. The .321 bores were common so hunters could shoot military 8mm S-bore rimless ammo; it was a compromise bore.
