The 380 ACP AMMO (9×17mm) (Automatic Colt Pistol) is a rimless, straight-walled pistol cartridge developed by firearms designer John Moses Browning. The cartridge headspaces on the mouth of the case. It was introduced in 1908 by Colt, for use in its new Colt Model 1908 pocket hammerless semi-automatic, and has been a popular self-defense cartridge ever since, seeing wide use in numerous handguns (typically smaller weapons). Other names for 380 ACP AMMO include .380 Auto, 9×17mm, 9mm Browning, 9mm Corto, 9mm Kurz, 9mm Short, and 9mm Browning Court (which is the C.I.P. designation). It should not be confused with .38 ACP.
The .380 ACP has experienced very widespread use in the years since its introduction (1908 United States, 1912 Europe). It was later adopted by the armies of at least five European nations as their standard pistol cartridge before World War II; Czechoslovakia (Vz.38), Hungary (FEMARU 37M), and Italy, all of whom used domestic designs, as well as The Netherlands and Yugoslavia, both of whom adopted the FN Model 1922. It was also use extensively by Germany, who capture hundreds of thousands of pistols in this caliber during WWII. Popular German built commercial models, such as the Walther PPK were very popular with German officers. The Italian Army used the Beretta M1934, but the Italian Air Force and Navy stuck with the 7.65mm/.32 ACP when they adopted the Beretta M1935.
While .380 ACP was considered to be a moderately powerful service pistol round before World War II when compared to the .32 ACP pistols it replaced, no nation retained it as a military service cartridge for very long after the war (when it was largely replaced by the more powerful 9×19mm Parabellum). It was widely use by police in Europe until 1970s when more powerful 9×19mm handguns began to replace it. The .380 ACP round is suitable for self-defense situations as a choice for conceal carry pistols. It was the round used in Defense Distributed‘s “Wiki Weapon” project to successfully 3D print a firearm.