The .32 ACP (Automatic Colt Pistol) pistol cartridge is a semi-rimmed, straight-walled cartridge developed by firearms designer John Browning, for use in the FN M1900 semi-automatic pistol. It is also known as the 7.65x17mm Browning SR or 7.65 mm Browning. Introduced in 1899 by Fabrique Nationale, the cartridge was first used in the Browning M1900.
John Browning engineered most modern semi-automatic pistol mechanisms and cartridges. As his first pistol cartridge, the .32 ACP needed a straight wall for reliable blowback operation as well as a small rim for reliable feeding from a box magazine. The cartridge was a success and was adopted by dozens of countries and countless governmental agencies. It has the distinction of being the cartridge that arguably ended World War II in Europe: Adolf Hitler reportedly committed suicide with an engraved .32 ACP Walther PPK.
The .32 ACP was designed for blowback semi-automatic pistols which lacked a breech locking mechanism. The relatively low power made it a practical blowback round. It is still used today primarily in compact, inexpensive pistols. Cartridges in .32 ACP are also sometimes used in caliber conversion sleeves, also known as supplemental chambers, for providing an alternative pistol caliber carbine functionality in .30-caliber hunting rifles.
The .32 ACP is compact and light, but short ranged, having marginal stopping power. Weapons chambered in it are often valued for their compactness and light weight relative to larger caliber pistols, particularly for concealed carry use. While able to kill, the the 65 or 71 grain low-velocity bullets do not incapacitate people readily. Hollow-point ammunition has been available for decades and may increase stopping power, although this is controversial. (In low-velocity usages, hollow-point bullets may not expand as expected. And, even if expansion does occur, stopping power may be more readily achieved and increased through deeper penetration by non-expanding FMJ bullets striking vital organs vs. shallow-wounding hollow-point bullets if the target is wearing heavy winter clothing.)
In Europe, the .32 ACP is more widely accepted than in America, having a long history of use for civilians as well as military and police agencies. The cartridge increased in popularity due to modern compact concealed carry pistols chambered for it, such as the Kel-Tec P-32, Beretta Tomcat and the Seecamp LWS 32. This increase in popularity has led many ammunition manufacturers to develop new, better-performing loads for the cartridge.