The .30 Carbine (7.62×33mm) is the cartridge used in the M1 Carbine introduced in the 1940s. It is an intermediate round designed to be fired from the M1 carbine's 18-inch (458 mm) barrel.
Shortly before World War II, the U.S. Army started a "light rifle" project to provide support personnel and rear area units more firepower and accuracy than the standard issue M1911A1 .45 ACP caliber handgun at half the weight of the M1 Garand rifle or the .45 Thompson submachine gun. The .30 Carbine cartridge was developed by Winchester and is basically a rimless .30 caliber (7.62 mm) version of the much older .32 Winchester Self-Loading cartridge of 1906 introduced for the Winchester Model 1905 rifle. The propellant was much newer, though, taking advantage of chemistry advances. The cartridge's relatively straight case and the rounded nose of its bullet led some to believe it was designed for use in pistols.
U.S. Army specifications for the new cartridge mandated the caliber to be greater than .27, with an effective range of 300 yards or more, and a midrange trajectory ordinate of 18 inches (460 mm) or less at 300 yards. With these requirements in hand, Winchester's Edwin Pugsley chose to design the cartridge with a .30 caliber, 100–120 grain bullet at a velocity of 2,000 feet per second (610 m/s). The first cartridges were made by turning down rims on .32SL cases and loading with .308 caliber bullets sharing a similar profile as the U.S. military .45 ACP bullet. The first 100,000 cartridges manufactured were headstamped ".30 SL".
