It was designed for early blowback pistols, that lacked a barrel locking mechanism.
It was the favored pistol cartridge for police use in Europe for many years, but has since been replaced by the much more potent 9 mm Luger.
Performance
The .380 ACP is compact and light, but short ranged and lacks stopping power. Even so it remains a viable self defense cartridge for use in compact pistols.
Muzzle velocity
6.2 g (96 gr) full metal jacket: 290 m/s (950 ft/s)
Notes
The .380 ACP should not be confused with the semi-rimmed .38 Auto (.38 ACP) round which was later developed into the potent .38 Super