The .308 Winchester (7.62x51mm) is a full power rifle cartridge. It was unveiled to the commercial market in 1952 by Winchester Repeating Arms Company, who also offered their Winchester Model 70 and Winchester Model 88 rifles in .308 Winchester.
The .308 Winchester was developed from the .300 Savage cartridge, and designed to give comparable performance to the .30-06 Springfield, but in a shorter cartridge.
The .308 Winchester is very similar to the 7.62x51mm NATO cartridge; they are nearly completely interchangeable and share the same dimensions (7.62x51mm).
The .308 Winchester is rimless. It uses a large rifle primer, and a .308 caliber (7.82mm) bullet. The bullet is 51mm long, and has an overall length (OAL) of 2.8 inches. The case has a capacity of 56 grains.
It is best fired from a barrel with a 1:12 rifling twist, and fires with a muzzle velocity between 2600 and 3300 feet per second, dependent on powder load, bullet weight, and barrel length. Bullet weights range from around 110 grains to 200 grains.
The .308 fires at a maximum pressure of 62,000 PSI (52,000 CUP). This is slightly greater than the pressure of the 7.62x51mm NATO cartridge.
Since the 7.62X51 NATO rounds are manufactured to a "looser" tolerance, the shooter sometimes has trouble using military surplus ammo in their commercial .308 Winchester chambers. The commercial chamber tolerances are tighter than the military. There is nothing wrong with either the rifle or ammo. It is just that the tolerances are different. If the loaded military round is run through a full length resizing die, it will enter easily in a commercial chamber.