I am thinking about getting a Mosin-Nagant 1891/30 and I am not sure what ammo to get. I have seen 7.62x54, 7.62x54r, 7.62nagant. Since they are listed seperatly I assume they are different, but I don't know for sure. Is 7.62x54r the only one that works in a Mosin-Nagant 91/30? What about the M44, does it use the 7.62x54r ammo as well?