I just got an M91/30 Mosin Nagant. It is an Izhevsk, 1942. I don't know much about it or shooting in general for that matter. Can anyone tell me if I can only shoot 7.62x54R cartridges or can I shoot any 7.62/.30 cartridges with it?

If a rifle is chambered in 7.62x54R then that is all you shoot in it. Unless you don't like you fingers and face.

Nice...lol...justlike the good ole 20-12 manicure....

I bought one at an estate sale several years back. It was one in a "lot" of firearms sold. It had already been expertly sported. I did not know anything about the information I might have gotten from the markings as folks have mentioned here.Never hunted with it., Just plinked. This one was a superb shooter so maybe it was one of the better ones theexperts here have mentioned. I did find the action weird. I gave it to a buddy of mine after his house was erased by Katrina.No flood insurance. He has used it now for 2 seasons. He has 13 deer with it. Most well under 100 yards andoneto about 150 yards ... no problem.I think he uses hunting ammo made by "Wolf", but I am not certain.