7.62x54R seem to be all over for sale. I have two, one that I chopped the stock and cleaned up for a deer rifle. The other I left ugly, bayonet and full wood stocks.
The Mosin Nagant rifles are OK, they are nothing to rave about. They are balisticly similar to a 30-06. Most ammo I find is cheap and either steel cased or FMJ surplus stuff. The old military stuff is always full of duds, I am sure it is real old.
I paid $100 for the pair I have.