9×17mm

The 9×17mm cartridge, also known by its commercial designation .380 ACP (Automatic Colt Pistol), is a rimless, straight-walled pistol cartridge developed by John Browning in 1908. It was designed for use in compact and subcompact semi-automatic pistols, offering a balance between manageable recoil and sufficient stopping power for self-defense.

The cartridge features a bullet diameter of approximately 9.0 mm (0.355 inches) and a case length of 17 mm (0.673 inches). While often confused with the 9x19mm Parabellum cartridge due to the similar bullet diameter, the .380 ACP is a significantly less powerful round. This reduced power contributes to its popularity in concealed carry firearms, as it allows for smaller, lighter, and more easily handled pistols.

The .380 ACP has seen widespread use by civilian shooters, law enforcement agencies for backup or off-duty use, and in military contexts in some countries. Its relatively low pressure and recoil make it a comfortable option for many shooters. Ammunition is widely available in various loadings, including full metal jacket (FMJ) for target practice and training, and jacketed hollow-point (JHP) for self-defense applications. The cartridge's effectiveness is generally considered adequate for close-range encounters, though it is often outclassed by more powerful service calibers.