Not really the same thing. 7.62X51 is safe to shoot in a .308 Win chamber but not vice-versa.Im pretty sure its the same thing. I think thats just the dimensions of the 308
^^^This! I have a remington 700 in .308, and an M1 Garand, re barreled in .308, and I have been shooting old surplus 7.62 NATO through both.Not really the same thing. 7.62X51 is safe to shoot in a .308 Win chamber but not vice-versa.
That is the exact opposite of .223 vs 5.56X45. .223 can be shot in a 5.56 chamber but you can't shoot 5.56 is a .223 chamber (safely).