What is ACP Ammo ?

This abbreviation stands for "Automatic Colt Pistol". Cartridges with the "ACP" designation are straight-wall cartridges that are all used in self-loading pistols. By definition, an ACP round is not used in revolvers or rifles, but are exclusively used in pistols.

ACP ammo is simply a type of handgun cartridge. The “ACP” part tells you it was designed for self-loading (automatic) pistols, rather than revolvers, and that it was developed by or for Colt.

 Common ACP Calibers

Here are the most well-known ACP cartridges:

Cartridge	Common Use	Bullet Diameter
.25 ACP	Pocket pistols, very small self-defense guns	0.251 in
.32 ACP	Compact concealed carry pistols	0.312 in
.380 ACP	Subcompact carry pistols	0.355 in
.45 ACP	Full-size pistols like the M1911	0.451 in
.38 ACP	Older semi-auto pistols (now largely obsolete)	0.356 in

Note: .380 ACP is also called 9mm Short, 9mm Kurz, or 9x17mm in different regions.

How is ACP Different From Other Ammo?

• ACP rounds are rimless or semi-rimmed, designed for smooth feeding in semi-auto pistols.

• They differ from revolver rounds like .38 Special or .357 Magnum, which are rimmed and not meant for semi-auto feeding.

• ACP cartridges typically have lower pressures than modern high-velocity designs (like 9mm Luger or .40 S&W), with the exception of .45 ACP which still has excellent stopping power.

Advantages of ACP Ammo

• Proven designs with long service histories

• Widely available (especially .45 ACP and .380 ACP)

• Compatible with many well-known pistols, including the Colt M1911, Walther PP series, Beretta models, etc.

.32 ACP

• Released: 1899

• Bullet Diameter: .3125 inches

• Case Length: .680 inches

• Bullet Weights: 60 to 75 grains

Designed by Browning, it was originally manufactured by Fabrique Nationale, a Belgian Company. This cartridge is often considered a European round. It becomes a popular rounds in the 20th century and often used by German police and popularly associated with James Bond movie.

.38 ACP (not to be mistaken with the .380 ACP)

• Released: 1900

• Bullet Diameter: .356 inches

• Case Length: 0.9 inches

• Bullet Weights: Roughly 115 to 130

.38 ACP is hard to find these days. You can find .38 Super rounds, but .38ACP have largely been left untouched by manufacturers due to little demand.

.38 Super phased out .38ACP, which is considered to have higher pressured version.

380 ACP

• Released: 1908

• Bullet Diameter: .355 inches

• Case Length: .680 inches

• Bullet Weights: Usually 80 to 120 grains

Not to be confused with the .38ACP or simply "thirty-eight", the .380ACP (Three-eighty) has been choosen as one of the popular self-defence round ever since its release.

.45 ACP

• Released: 1905

• Bullet Diameter: .452 inches

• Case Length: .898 inches

• Bullet Weights: 100 to 230 grains

The .45ACP is one of the few "ACP" cartridges created specifically for military purposes. To these days, the .45ACP remains one of the most chosen pistol cartridges around the world especially in America. Used by tactical forces, military personnel, and sports shooters.

It was commonly used by US Army in Vietnam war and WW-2 for sidearm.

If you see ACP on a box of ammo or stamped on a barrel, it just means the cartridge is part of the Automatic Colt Pistol series — a family of tried-and-true rounds that helped define the modern semi-automatic pistol.