The .308 Winchester is a smokeless powder rimless bottlenecked rifle cartridge. The exterior shape of the case was designed to promote reliable case feeding and extraction in bolt action rifles and machine guns alike, under extreme conditions.
The .308 Winchester is one of the most popular hunting cartridges in the United States, and possibly the world.[citation needed] It has gained popularity in many countries as an exceptional cartridge for game in the medium- to large-sized class.[16] In North America it is used extensively on whitetail deer, pronghorn and even the occasional caribou or black bear.
Although not identical, the .308 Winchester and military 7.62×51mm NATO cartridges are similar enough that they can be loaded into rifles chambered for the other round, but the .308 Winchester cartridges are typically loaded to higher pressures than 7.62×51mm NATO service cartridges.[12] Even though the Sporting Arms and Ammunition Manufacturers' Institute (SAAMI) does not consider it unsafe to fire the commercial .308 Winchester rounds in weapons chambered for the military 7.62×51mm NATO round, there is significant discussion about compatible chambers and muzzle pressures between the two cartridges based on powder loads, chamber dimensions and wall thicknesses in the web area of the military compared to commercial cartridge cases.[13][14] As the chambers differ accordingly the head space gauges used for the two chamberings differ.[15]