RE: 7.62x54R question
Not that I'm aware of. You'd probably be able to have a custom barrel chambered for it, but that would be a very expensive complicated approach to a problem with a much cheaper and easier solution.
Buy a .30-06.
Just about every rifle manufacturer chambers for it, it'll outperform the 7.62x54R by a significant margin in all bullet weights, high quality ammo is readily available, including the premium ammo. The 7.62x54R is an obsolescent cartridge that enjoys marginal popularity here in the west solely because of the availability of super-cheap surplus Mosin-Nagant rifles, most of dubious quality, and ultra-cheap surplus and steel-cased imported ammo. A fine rifle if you want to shoot a CF on the cheap and burst milk jugs at 50 yards. If you want a serious .30 cal hunting rifle with accuracy you can count on, a recent production sporting rifle in .30-06 is the way to go. 4-5MOA from a surplus Mosin is not good enough IMO. I want a rifle that is accurate enough that if I miss I can know for sure it's not the rifles fault...3 MOA MAX, with 1.5MOA or less average being my preference.
Mike