The bullet is the same size, but the cases are different.Lots of Russian rifles are chambered for 7.62 mm including the very nice Dragunov sniper rifle. Yeah the Russian 7.62mm is a little more heavy load but all those rifles will still fire the 7.62 NATO round.
The M1891 Mosin Nagant rifle (I have 4, 2 Russian, 2 Finnish M-39) and SVD Draganov (I have a Dragunov Tiger, short barreled civilian import). They fire a 7.62 X 54R round (54mm long, rimmed case).
Strange that you'd have a somewhat modern squad support rifle fire a round that was developed in 1891! (I guess if it ain't broke comrade, don't fix it...)
The NATO 7.62 X 51 (308 Winchester) (51mm long case, not rimmed).