The .45 ACP (Automatic Colt Pistol) is a popular handgun cartridge developed by John Browning in 1905. It is known for its large diameter bullet, typically measuring .452 inches, and is designed for semi-automatic pistols. The .45 ACP is favored for its stopping power and manageable recoil, making it a common choice for self-defense and law enforcement. This cartridge is widely used in various firearms, including the iconic M1911 pistol, which has been a staple in military and civilian use for over a century. The .45 ACP is also popular in competitive shooting and is available in various bullet types and loads to suit different shooting needs.