No Comments What does ACP stand for and what is ACP ammo? If you’ve ever shopped for ammo or looked into the different pistol calibers, you’ve come across the ACP acronym.
Today we’re exploring what ACP ammo is and looking at the different ACP calibers.
What is ACP Ammo?
The acronym “ACP” stands for Automatic Colt Pistol. This designates select cartridges designed by legendary firearms designer John Moses Browning. Browning’s ACP cartridges are straight-wall designs for his self-loading semi-auto pistols.
The ACP cartridges are .32 ACP, .38 ACP, .45 ACP, .25 ACP, and .380 ACP.
Breaking it Down
The “A” in “ACP” stands for automatic. This refers to automatic pistols, though in modern times we refer to them as semi-autos.
Next, the “C” stands for Colt, the gun manufacturer that Browning worked for at the time. Including the company name behind the cartridge was, and still is, common practice. For example, Smith & Wesson is behind the .40 S&W cartridge.
Finally, the “P” stands for Pistol. This denotes that the cartridge is specifically designed for pistols.
What are the ACP Cartridges?
Now, let’s take a look at the ACP cartridges.
The ACP cartridges are:
- .32 ACP
- .38 ACP
- .45 ACP
- .25 ACP
- .380 ACP
- .32 ACP
.32 ACP
- Designer: John Browning
- Designed: 1899
- Bullet Diameter: .3125”
- Overall Length: .984”
- Other Names: .32 Auto, .32 Automatic, 7.65mm Browning, 7.65x17mmSR
The .32 ACP is the first of the ACP cartridges. John Browning designed the .32 ACP for use in the Fabrique Nationale FN M1900 semi-automatic pistol. The cartridge uses a straight wall and small rim to enable reliable blowback operation and feeding from a box magazine.
The .32 ACP quickly gained popularity, and other gun manufacturers produced guns chambered for the cartridge in the years following its release.
.38 ACP
- Designer: John Browning
- Designed: 1900
- Bullet Diameter: .356”
- Overall Length: 1.28”
- Other Names: .38 Auto, .38 Automatic, 9x23mmSR
Not to be confused with the .38 Special, Browning designed the .38 ACP shortly after the .32 ACP for the Colt M1900. The M1900 was the first handgun to use a short-recoil operation, and influenced the design of the M1911.
While the .38 ACP is not a common cartridge today, it is the reason we have the .38 Super cartridge. The .38 Super uses the same dimensions as the .38 ACP but is loaded to a higher pressure. For this reason, it’s not safe to shoot .38 Super ammo in .38 ACP guns.
.45 ACP
- Designer: John Browning
- Designed: 1904
- Bullet Diameter: .452”
- Overall Length: 1.275”
- Other Names: .45 Auto, .45 Automatic
The .45 ACP is the most powerful and likely the most popular of the ACP cartridges. As is true with all the ACP rounds Browning designed, the .45 ACP was designed for use in his prototype Colt semi-auto pistols. In 1911, the U.S. Military adopted the round for use in the Colt M1911 pistol which served as the standard-issue sidearm between 1911 and 1985.
The .45 ACP cartridge is still extremely popular, though many shooters opted for less-powerful pistol cartridges like the 9mm and .40 S&W as bullet designs improved over the years. However, the 1911 and other .45s are still mainstream choices for shooters.
.25 ACP
- Designer: John Browning
- Designed: 1905
- Bullet Diameter: .2512”
- Overall Length: .910”
- Other Names: .25 Auto
Browning introduced the .25 ACP cartridge with the Fabrique Nationale M1905 pistol, which inspired the nearly identical Colt Model 1908 Vest Pocket pistol, and the later Baby Browning. Browning designed the .25 ACP because it was the smallest cartridge he could make while retaining a centerfire primer pocket which was more reliable than rimfire primers.
The cartridge became extremely popular due to the many “pocket pistols” or “mouse guns” that were eventually chambered in caliber. Today, it’s not too common that you come across someone carrying a .25 ACP pistol. Shooters often view the .25 ACP as underpowered and opt for more modern cartridge designs.
.380 ACP
- Designer: John Browning
- Designed: 1908
- Bullet Diameter: .355”
- Overall Length: .984”
- Other names: .380 Auto, .380 Automatic, 9x17mm, 9mm Kurz, 9mm Browning Short, 9mm Browning, 9mm Corto, 9mm Short, 9mm Browning Court
Of the more popular ACP rounds is the .380 ACP, which Browning based off of the slightly more powerful .38 ACP. Browning designed it for use in the Colt Model 1903 Hammerless semi-auto pistol. The popularity of the .380 ACP exploded, and many governments picked up the pistol cartridge for law enforcement and military use. While the .380 ACP is not the most powerful pistol cartridge, many found that the round was still feasible for self defense, and offered smaller, lightweight gun options that were worth the trade off.
The .380 ACP is still a popular cartridge today and you can find many modern pistols chambered in the caliber. For example, Smith & Wesson currently offers two .380 ACP pistols: the M&P 380 Shield EZ and the smaller Bodyguard. Along with many pistol options, shooters also have a good selection of .380 ACP ammo from major manufacturers.
Final Thoughts
It’s impressive that ammo and firearms designs by John Moses Browning, like the 1911 and ACP cartridges, are still relevant today. And now that you know the history behind the ACP designation, you can give a nod to John Browning the next time you pick a box of .380 ACP ammo or .45 ACP ammo!
