Question: what is the difference between .308 and 7.62 x51?
Answer: 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.