I'm very familiar with the rifle the guy loaned you. You have a Mosin Nagant M44, with the fold out bayonet. Yours is most likely Russian, although some were made in Poland. The year of the rifle will be stamped between the receiver and the rear sight on top of the gun. I use a customized Mosin Nagant (not the same model as yours) for deer hunting. To adjust that rifle for windage you have to drift the front sight, and the rear sight is set for meters. Although it will most likely shoot high at 100 yards. The 500 rounds you have are probably military surplus, but I dont know because you didn't specify. Those are NOT suitable for hunting as they would be FMJ, you need soft point bullets. You may just want to invest in a Marlin bolt action rifle for your sons. The Marlin bolt actions are fairly cheap but they're a nice rifle. The 7.62x54R round is basically the same as a the .308 cartridge, but they are not interchangeable by any means.