the 7.62 is a light loaded .308 you can use it in a 308 gun but you should not use the 308 in a 7,62 only gun

Michael, A 7.62 x 51 or 7.62 NATO round is a .308 round basically. We could go down the rabbit hole on loads, power, bullet types, etc. But basically the same. Besides the pressure difference of about 63,000 psi on .308 and 50,000 psi on 7.62 NATO the 7.62 NATO has thicker case walls. They also head space a couple of a hundredths of a thousands differently. 308 Win headspace is between 1.630 and 1.6340 inches while the 7.62 NATO is between 1.6355 and 1.6405 inches. The published numbers place the difference within six-thousandths of an inch, but surplus 7.62 rifles can be anywhere from 10 to 15 thousandths longer than a commercial . 308 Win.

Michael, they are interchangeable dimension wise but .308 is loaded to a higher operating pressure than the Military 7.62x51 ammunition. It is the opposite of 5.56 vs .223 where the Military 5.56 is loaded hotter.

I am no expert but, I can shoot either in my 308. 7.62 is a nato designation.