Introduced by John Browning in 1905, the .25 Automatic Colt Pistol (ACP) cartridge was designed to be fired in the Fabrique Nationale Model 1905 pistol (6.35x16mmSR). This was a centerfire “vest pocket” pistol, made for gentlemen who needed their firearms to remain undetectable. But among other bad press, some firearms authorities dismissed the small caliber as a "mouse gun." The .25 ACP is lethal, however, and firearms in this caliber should be treated with the same respect as larger caliber weapons.
Small, inexpensive firearms intended for concealed carry in a pocket or small handbag are the primary weapon chambered for .25 ACP, which enjoys several advantages as a concealed carry pistol. The first is its small size, making concealment much easier than with larger handguns in a variety of situations and locations (a standard size .25 ACP is smaller than even the smallest 9mm pistols). With a centerfire primer, it's more reliable than .22 LR rimfire cartridges, which are found in similar-sized pistols. An abundance of self-protection loads are available for the .25 ACP, which are worth consideration with recent advancements in technology – maximizing bullet penetration and expansion like a jacketed hollow point (JHP).
Many firearms have been chambered for the .25 ACP cartridge, including several revolvers as well as antiques manufactured in Belgium or Italy. The unique Lercker pistol was designed to fire the .25 ACP, was fully automatic with a 20-round magazine, and fired 1,200 rounds per minute. It was not produced widely, yet this interesting pistol sheds new light on the .25 ACP as a self-defense cartridge.
Firearms enthusiasts either love or hate the .25 ACP, but its many fans throughout the world are why manufacturers continue to produce firearms in this caliber. Ammo manufacturers also continue to produce volumes of practice ammo and include it in their self-defense product lines. With mild recoil and acceptable accuracy and reliability, the .25 ACP will continue to be used for backup and deep concealment needs for a long time to come.