I have a Norwegian Rolling Block, date stamped 1877. It is not a 50-70 gov. the bore at the muzzle is 12.03 mm or 0.485 ". The groove diameter at the muzzle is 13.06 mm or 0.497 ". What caliber is this? Are bullets in this size available anywhere? How about reloading dies? The 50-70 gov case fits the chamber. Confused.