.32 ACP

It was designed for early blowback semi-automatic pistols which lacked a breech locking mechanism; the relatively low power of the .32 ACP round made it a practical blowback round. It is still used today in blowback semi-automatic pistols, as well in modern locked-breech, single column magazine, deep-concealment, semi-automatic 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. In the United States, it has long been considered by some to be inadequate for self defense because of its limited penetration ability. Others in the United States consider .32 ACP to be the bare minimum for self defense because of its limited power, rating in the 65% range for single shot stops compared with larger calibers such as the .357 magnum and .45 ACP which rank in the 90% range. FMJ ammunition is required to meet the FBI's requirement of 12" to 18" penetration in calibrated tissue simulant; hollowpoint ammunition which successfully expands is not able to meet this requirement in .32 ACP.

In Europe, the .32 ACP is more widely accepted, having a long history of use for civilians as well as military and police agencies. The cartridge has had somewhat of a recent upsurge in popularity due to some very compact and lightweight concealed carry pistols chambered for it, such as the Kel-Tec P-32 and the Seecamp LWS 32. This increase in popularity has led many ammunition manufacturers to develop new, better-performing loads for the cartridge. The bullet that Gavrilo Princip used to assassinate Franz Ferdinand was from a .32 ACP cartridge.

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