.45 Auto (ACP)

The .45 Auto (ACP), also known as the .45 Automatic Colt Pistol, is a popular centerfire handgun cartridge that was developed by John Browning in the early 20th century. It was designed to be used in the Colt M1911 pistol, which was adopted by the US military as its standard-issue sidearm from 1911 to 1986.

The .45 ACP cartridge has a bullet diameter of .451 inches (11.5 mm) and a case length of .898 inches (22.8 mm). It is a powerful cartridge that has a reputation for its stopping power, with a typical muzzle velocity of around 850 to 1000 feet per second (260 to 305 m/s) and a muzzle energy of around 350 to 550 foot-pounds (475 to 750 J).

The .45 ACP is widely used by law enforcement and military personnel, as well as civilian shooters for self-defense and target shooting. It is also used in various firearms platforms, including semi-automatic pistols, revolvers, and submachine guns. Despite the introduction of newer cartridges with higher velocity and energy, the .45 ACP remains a popular and respected cartridge among firearms enthusiasts.