The .45 Long Colt (LC) and the .45 Automatic Colt Pistol (ACP) and are not near as similar as they sound. Putting .45 LC in a firearm designated for .45 ACP isn’t going to work out for you. That’s because one goes in a revolver and the other in a semi-automatic pistol. This blog will dive into a few of the key differences between the two: .45 LC vs. .45 ACP.
.45 Long Colt Ammo
Despite Colt being in the names of both LC and ACP, they are quite different.
Way back in 1872, Colt and the Union Metallic Cartridge Company decided to partner up and create the .45 Long Colt, sometimes written as .45 LC, adopted by the U.S. Army in the following year.
The army shot the .45 LC through their Colt Single Action Army Revolver until they decided they wanted semi-auto pistols, in which case they needed a new firearm and a new round.
.45 ACP Ammo
That’s when .45 ACP, also commonly called .45 Auto, came about. In 1904, John Browning developed the .45 ACP, not Colt like the name tends to imply. Although Browning did work for Colt at the time.
The U.S. Army Transitions from .45 LC to .45 Auto
Because the army wanted a semi-auto without giving up the power and accuracy they had with their revolvers, they went with what the Tompson-LaGarde tests told them was the most effective, the .45 caliber. So, the Army decided to keep the .45 — ACP for a semi-auto pistol, shot through Browning’s 1911.
.45 LC vs. .45 ACP
What else is different besides manufacturers of the time? Well, visually, they also look different. The .45 Long Colt looks longer than the ACP. And the LC has a .452″ diameter bullet over the .451” diameter of the ACP bullet.
At first, hearing about .45 ACP, it’s easy to think using the term .45 auto is just a shortening of saying the entire thing. But, that’s not entirely true. It might be why you or your gun buddies say it that way, but there’s an actual reason other than the simplicity, and that has to do with something known as SAAMI.
SAMMI stands for Sporting Arms and Ammunition Manufacturers’ Institute. They standardize the shooting industry. And since they’re in the business of standardizing, you can imagine that they probably have multiple rules. One of those rules is that they don’t accept trademarked cartridge names. But, that doesn’t mean they won’t accept an identical product with a non-trademarked name.
For instance, and how we get back into ACP, SAAMI wouldn’t accept the Copywrite, .45 ACP, but they would consider a .45 automatic or .45 auto because there’s no Copywrite attached to it.
International .45 ACP Names
There are many different names for .45 ACP, the most common in the U.S. is .45 ACP, .45 auto, or .45 automatic. However, if you venture outside of the states, you’ll find 11.43×23 mm, 11 mm 43, and 11.25mm.
Can You Shoot .45 ACP and .45 LC Through the Same Firearm?
Here’s the most important thing you need to take away from this article: .45 Long Colt and .45 ACP are NOT interchangeable. LC is meant for your revolver, and ACP is intended for your semi-auto. It’s never a good idea to try and shoot ammunition through a weapon that it isn’t designed to fire. Depending on the caliber, you could severely damage your gun or yourself. For instance, trying to shoot a .44 magnum through your .45 colt could blow your gun up.
Please keep in mind, even if a cartridge fits, that doesn’t mean you should load it.