Anyone interested in firearms and ammunition, especially pistols, will inevitably come across the acronym ACP ammo. This abbreviation stands for “Automatic Colt Pistol,” and designates cartridges used in a specific, and rather historic, type of firearm.
Whether you are a seasoned firearms expert or just learning the basics, knowing the background of the term “ACP” is not only interesting, it will make you a more informed buyer of åfirearms and ammunition.
What Is ACP Ammo?
As we noted, the term “ACP” comes from “Automatic Colt Pistol.” It was a designation created to mark the engineering of John Moses Browning. Known as one of the most influential weapons designers of all time.
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.
The ABCs of ACP
The first letter, “A,” stand for “automatic.” This notes that the rounds are made for “automatic” pistols. Although under today’s definitions they are technically semi-automatic weapons.
The second letter, “C,” is for Colt. At the time, Browning was working for the Colt Manufacturing Company. Adding the company name to the cartridge was, and still is, a common practice.
Finally, the “P” notes that the rounds are made for pistols. Not revolvers, not rifles, but pistols. This may seem redundant since “automatic” is already included, but that’s the logic behind the naming.
A Brief Look At “ACP” Cartridges
- Released: 1899
- Bullet Diameter: .3125 inches
- Case Length: .680 inches
- Bullet Weights: 60 to 75 grains
The earliest cartridge that eventually took the ACP name was this well-balanced round. Although it was released at the end of the 19th century, it becomes one of the most influential rounds in the 20th century.
Designed by Browning, it was originally manufactured by Fabrique Nationale, a Belgian company. This cartridge if often considered a European round. Often associated with James Bond, German police, and, historically, the suicide of Adolf Hitler. However, it has found use as a conceal-carry round and plinking cartridge in the United States.
- Released: 1900
- Bullet Diameter: .356 inches
- Case Length: 0.9 inches
- Bullet Weights: Roughly 115 to 130
The .38 (not to be mistaken with the .380 ACP) was paired with the innovative M1900. This pistol was the first to use the short-recoil operation, now commonly called self-loading. While the operating system of the firearm was game-changing, the cartridge itself was underwhelming. It never gained large popularity. It was largely phased out by the .38 Super, which is essentially a high-pressure version of the .38 ACP.
Today, the .38 ACP is rare. You can find .38 Super rounds, but .38 ACPs have largely been left untouched by manufacturers due to little demand.
- Released: 1905
- Bullet Diameter: .251 inches
- Case Length: .615 inches
- Bullet Weights: 30 to 50 grains
Thin and light, the .25 ACP is a versatile round that was originally created to compete with the .22 Long Rifle, replicating the .22’s performance when fired from a two-inch barrel. Because of the cartridge’s small dimensions, it could be loaded into some of the most compact weapons ever made. However, it was weakly powered and is generally considered a poor performer.
Although sales were light, the .25 ACP was tried in numerous firearms. A few military organizations tried small machine guns with this cartridge. Somewhat ironically, there were even a few revolvers released that were chambered for this cartridge.
- Released: 1908
- Bullet Diameter: .355 inches
- Case Length: .680 inches
- Bullet Weights: Usually 80 to 120 grains
Not to be confused with the .38 ACP (“thirty-eight”), the .380 ACP (“three eighty”) has been a popular self-defense round ever since its release. It has a slightly smaller profile than the .38, yet maintains consistent power and performance.
There is a concern, however, that the .380 ACP is inadequate for defense purposes. While others tout its ability to be loaded into compact weapons. It’s often considered the lightest acceptable round for self-defense.
- Released: 1905
- Bullet Diameter: .452 inches
- Case Length: .898 inches
- Bullet Weights: 100 to 230 grains
John Browning is known for creating the M1911, which chambered the .45 ACP. This handgun is now seen in numerous “1911-style” handguns, which are effective weapons to this day. A large reason that this gun was so popular, and has become replicated by virtually all manufacturers, is because of the .45 ACP.
The .45 ACP is one of the few “ACP” cartridges created specifically for military purposes. After recognizing a need for greater performance from their ammunition, the U.S. military commissioned a series of tests and trials, allowing various manufacturers to offer their designs. After a long process, the .45 ACP, along with the M1911, was chosen.
To this day, the .45 ACP remains one of the most popular pistol cartridges in America. Used by tactical forces, military personnel, and sports shooters, this ACP round can deliver power and ballistic performance to the target in almost any setting.
“Auto” Or “Colt” Does Not Automatically Mean “ACP”
Cartridges often go by multiple names. The .45 ACP, for example, is also known as the “.45 Auto,” and is sometimes just called the “forty-five.” Many rounds, in fact, are called “auto” and most of the ACP rounds can be found under this terminology. Some manufacturers don’t list the “.380 ACP,” but instead list it under .380 Auto. (Cartridge naming is tricky; at times it seems like the manufacturers are intentionally trying to confuse people.)
However, the presence of the word “auto” does not mean that the round is necessarily an “Automatic Colt Pistol” round. For example, the 10mm Automatic, or “10mm Auto,” is not a round that falls under the “ACP” designation.
Likewise, not all “Colt” rounds are ACP either. The .45 Colt was, as the name notes, created by Colt’s Manufacturing Company. But it’s for revolvers and lever-action rifles. Not for pistols. It is, therefore, not an ACP.
ACP Ammo For Sale
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