762×51

The 7.62×51mm NATO cartridge, often written as 7.62×51 or 7.62 NATO, is a rimless, bottleneck rifle cartridge designed in the post–World War II era to standardize power and performance for NATO forces. Developed through international collaboration, it was adopted as the NATO standard in the early 1950s and subsequently used by many member nations in service rifles and medium machine guns. It replaced several earlier country-specific rounds, notably the .30-06 Springfield, in a wide range of weapons such as the M14 rifle, FN FAL, and HK G3.

Design and performance: The cartridge is a .30 caliber (7.62 mm) bottleneck with a case length of about 51 mm and an overall length around 68–69 mm. Standard service ammunition has been a 147-grain full metal jacket bullet (M80), with muzzle velocities typically in the 2,500 to 2,800 feet per second (about 760 to 850 meters per second) range, yielding muzzle energies roughly between 2,400 and 3,000 joules depending on the loading and firearm.

Variants and use: Over the years a variety of ammunition types have been developed, including tracer, armor-piercing, and longer-range match rounds. The 7.62×51 remains in use today in designated marksman rifles, later-designated long-range sniper rifles, and various machine guns in many countries. While many armed forces have transitioned part of their inventories to smaller calibers such as 5.56×45, 7.62×51 NATO continues to serve in roles where greater downrange energy or heavier bullets are advantageous.

Interchangeability notes: The 7.62×51 NATO and .308 Winchester are dimensionally similar but not identical; NATO specifications call for lower maximum pressures. Some firearms can safely chamber and fire both, but compatibility depends on weapon design and should follow manufacturer guidance.