.45 Long Colt vs. .45 ACP Ammunition

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

.45 Long Colt
.45 Long Colt/Photo Credit: Malis/Wikimedia Commons

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

45ACP Ammunition
Several .45 ACP variants: hollow point, full metal jacket, WWII-era military issue birdshot/Photo Credit: Derek280/Wikimedia Commons

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 Primary Arms
Prices accurate at time of writing

There are some other, less exciting details, and I might lose some of our newer shooters here, but the grain, muzzle velocity, and muzzle energy are different too.

.45 Long Colt Specs

  • 250-grain bullet
  • 860 fps muzzle velocity
  • 411 ft/lbs muzzle energy

.45 ACP Specs

  • 230-grain bullet
  • 850 fps muzzle velocity
  • 369 ft/lbs muzzle energy

Which is more powerful, .45 Long Colt or .45 ACP?

So, what do all those numbers translate into? Basically, it means Long Colt is more powerful than ACP. Which presents a new question, why go to a .45 ACP when you get more power shooting .45 LC?

The answer was that it’s easier and quicker to reload a semi-auto when you’re rushed than it is a revolver. This is why, even today, the semi-auto is generally favored over the revolver.

Ammo Inc .45 ACP tracer
Ammo Inc .45 ACP tracer

Often laughed at, but a reason nonetheless, is the additional round capacity. You get a load of 7 in 1911 magazines over the 6 shots in revolvers. 

at Primary Arms
Prices accurate at time of writing


What are the Different Names for .45 ACP?

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.

Sig Sauer .45 ACP V-Crown Performance
Sig Sauer .45 ACP V-Crown Performance


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.

at Gorilla Ammunition
Prices accurate at time of writing

Table of Contents

  • .45 Long Colt Ammo
  • .45 ACP Ammo
  • The U.S. Army Transitions from .45 LC to .45 Auto
  • .45 LC vs. .45 ACP
  • .45 Long Colt Specs
  • .45 ACP Specs
  • Which is more powerful, .45 Long Colt or .45 ACP?
  • What are the Different Names for .45 ACP?
  • International .45 ACP Names
  • Can You Shoot .45 ACP and .45 LC Through the Same Firearm?

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