The 7.62×51mm NATO (official NATO nomenclature 7.62 NATO) is a rimless bottlenecked rifle cartridge developed in the 1950s as a standard for small arms ...
Bullet diameter: 0.308 in (7.82 mm)
Case length: 2.015 in (51.2 mm)
Rifling twist: 1 in 12 in (304.8 mm)
Used by: NATO and others