The .30 Carbine is the cartridge

Cartridge (firearms)

A cartridge, also called a round, packages the bullet, gunpowder and primer into a single metallic case precisely made to fit the firing chamber of a firearm. The primer is a small charge of impact-sensitive chemical that may be located at the center of the case head or at its rim . Electrically...

 used in the M1 Carbine

M1 Carbine

The M1 carbine is a lightweight, easy to use semi-automatic carbine that became a standard firearm for the U.S. military during World War II, the Korean War and the Vietnam War, and was produced in several variants. It was widely used by U.S...

 introduced in the 1940s. It is an intermediate round designed to be fired from the M1 carbine's 18-inch (458 mm) barrel.
The .30 Carbine cartridge and the M1 Carbine were developed by Winchester

Winchester Repeating Arms Company

The Winchester Repeating Arms Company was a prominent American maker of repeating firearms, located in New Haven, Connecticut. The Winchester brand is today used under license by two subsidiaries of the Herstal Group, Fabrique Nationale of Belgium and the Browning Arms Company of Morgan, Utah.-...

 and the U.S. Army to provide assault troops and rear area units more firepower and accuracy than the standard issue M1911A1 .45 ACP

.45 ACP

The .45 ACP , also known as the .45 Auto by C.I.P., is a cartridge designed by John Browning in 1904, for use in his prototype Colt semi-automatic .45 pistol and eventually the M1911 pistol adopted by the United States Army in 1911.-Design and history:The U.S...

 caliber handgun and .45 Thompson submachine gun

Thompson submachine gun

The Thompson is an American submachine gun, invented by John T. Thompson in 1919, that became infamous during the Prohibition era. It was a common sight in the media of the time, being used by both law enforcement officers and criminals...

.