Too many cartridges wound up with similar names despite being totally different from one another. We often have shooters ask us if they can fire 38 Super in their 38 Special revolvers. It’s perfectly fair of them to wonder if they could – “super” and “special” are similar concepts, after all, and it doesn’t help when they’re preceded by the same number.
On the flip side, too many cartridges also have multiple, dissimilar sounding names. We get plenty of people asking if they can fire 9mm in a Glock 17 with “9×19” engraved on its barrel. Perhaps no two rounds’ names lead to more confusion than the 45 Long Colt vs. 45 Automatic Colt Pistol (ACP). We dread getting the phone call:
“Why won’t this ammo I ordered from you fit in my 1911?” We know the answer before they say anything further: “You got the wrong ammo!”
The Difference Between 45 Long Colt vs. 45 ACP
45 Long Colt
The 45 Long Colt was developed in 1872 in partnership by Colt and the Union Metallic Cartridge Company, which is now a subsidiary of Remington. Originally a black powder round by necessity, the U.S. Army adopted 45 Long Colt in 1873. It served as the official handgun round for their Colt Single Action Army revolver for 14 years.
45 ACP
John Browning developed the 45 ACP in 1904. At the time the Army wished to replace their revolvers with semi-automatics, but naturally without sacrificing accuracy or power in the process. As the Thompson-LaGarde Tests of 1904 had determined .45 caliber to be the most effective pistol cartridge, Browning kept that bullet.
Browning’s 1911 pistol remained the main sidearm of the U.S. military until its replacement by the Beretta M9 in 1985 and then the 9mm SIG Sauer P320 in 2017. The primary difference between the 45 Long Colt and 45 ACP is readily apparent: One is designed for a revolver, while the other is designed for a semi-auto. The 45 Long Colt’s shell casing thus features a rim that enables it to sit securely in a cylinder.
While plenty of semi-autos can handle rimmed cartridges – the 22 LR being the most popular that comes to mind – rims are generally considered a detriment to smooth feeding and extraction. While 45 ACP ammo technically does have a rim, its rim diameter is eight times smaller than that of the 45 Long Colt’s when you compare the rim’s protrusion to the base diameter of the cartridge.
As a dedicated semi-auto cartridge, the 45 ACP features an extractor groove that provides a surface for a handgun’s extractor to purchase against during extraction. You will not find such a groove on a revolver cartridge. If you would rather differentiate the two cartridges by their lengths alone, the 45 Long Colt is 0.325” longer.
The Similarities Between 45 Long Colt and 45 ACP
A close-up shot of 45 Long Colt ammo on the left and 45 ACP ammo on the right.
John Browning didn’t set out to create an entirely different cartridge than that which the U.S. Army had become accustomed to. He actually developed the 45 ACP to match the ballistics of the 45 Long Colt fairly closely! It’s not an apples to apples comparison, though. A typical 45 Long Colt cartridge has a 250 grain bullet and 860 fps muzzle velocity, giving it 411 ft lbs muzzle energy.
In comparison, a standard 45 ACP cartridge has a 230 grain bullet and 850 fps muzzle velocity, giving it 369 ft lbs muzzle energy. The 45 Long Colt is effectively a more powerful cartridge, but with a 1911 you get seven shots in the magazine instead of six in the cylinder. It’s a lot easier to reload a semi-auto than a revolver when you’re in a hurry, too, which is why they’re generally more favored. The 45 Long Colt has a .452” bullet.
The 45 ACP, on the other hand, has a .451” bullet. If you consider one one-thousandth of an inch a great length, then you may argue that the two cartridges’ bullets are in fact very different from one another. It’s going to be a tough sell, though.
The Takeaway
It’s dangerous to mistake some rounds for others when they share identical dimensions yet create very different chamber pressures. That’s why you should take every precaution against running 5.56×45 through a rifle chambered only for 223 Rem, and why you also don’t want to run 9mm +P+ through an original Luger pistol.
Fortunately, you’re not likely to mistake a rimmed 45 Long Colt for a rimless 45 ACP. They simply look too dissimilar to permit such a mix-up. Simply avoid buying 45 ACP for your Single Action Army, or 45 Long Colt for your semi-auto, and you’ll be safe. The only difficult task remaining will be actually hitting your target!
“Browning’s 1911 pistol remained the main sidearm of the U.S. military until its replacement by the 9mm SIG Sauer P320 in 1985.” – Really? Because I was in the Army from 1988 until 1996 and my MOS was 19K armor crewman. This MOS is one in which qualification with a side arm is required. I recall being trained on the Beretta M9 9MM at Ft. Knox Kentucky, then being trained and qualified on the 1911A1 at my first duty station because the M9 was still replacing old faithful. It’s errors like these where you fire the editor that reviewed this story because the reputation is now reduced in my opinion. Epic fail…
Consider him fired and his children eliminated Aaron.
Not so fast. Anyone who has served in the military knows that just because an item is replaced, the period it takes to fully replace the old item is usually years. Even after the new item is in service, the replaced version is often kept around for various reasons.
lmfao
We went from the 1911, to the beretta and then to the sig so maybe he got things messed up by order? Don’t know
In my 30+ years in airborne infantry, mostly in Ranger and SF units as both an NCO and later commissioned officer, we used the old M1911A1 as a regulation sidearm until the Berettas showed up in the mid-1980s. HOWEVER, in Ranger BNs back in the old days (unofficially) and in SF Groups (allowed) we almost always carried as personal sidearms either the Browning P-35 Hi- Power or Beretta 92FS (aka M9) with hi-capacity mags. Also both the Browning and Beretta had/ have barrels that protrude past the slide, allowing them to be threaded for silencers when needed. I retired with well over 30 years in 2004 (5 1/2 years in combat) so I can’t say what happened later. However, in MY experience I don’t recall ANYONE using a Sig as a personal weapon, or for them to have been in our inventories
Aaron said: “Browning’s 1911 pistol remained the main sidearm of the U.S. military until its replacement by the 9mm SIG Sauer P320 in 1985.”
What was actually said: “Browning’s 1911 pistol remained the main sidearm of the U.S. military until its replacement by the Beretta M9 in 1985 and then the 9mm SIG Sauer P320 in 2017.”
You owe us 1000 push-ups. Get crackin’, boot.
He said Sig in 2017. Reread it.
You should reread what the article says vs what you are b******* about. You sir are incorrect. Please wait for the natural light to wear off before commenting in the future
Who cares
It’s say Beretta m9 1985 sig Sauer 2017
The article states the the U.S. military went directly from the 1911 directly to the Sig P320, skipping right over the less than stellar Italian wannabe.
Yep, you’re right. Sorry about that. Got so excited to get to the present that we jumped that middleman.
Reread it didn’t skip the m9
I’m not sure but wasn’t it the mod 92 that was the first after the 1911?
Technically the M9 slid in there between the 1911 and the Sig — thanks for the heads up Erik.
You wrote ” While 45 ACP ammo technically does have a rim, its diameter is eight times smaller than that of the 45 Long Colt’s.”
What?? Eight times anything is bigger..1/8 of is smaller..What or how are you measuring??
My 45ACP rim diameter is ,475 inch, my .45 Colt cowboy loads measure .508 inch dia.
Hi Bunker – the measurement is how large the rim diameter is relative to the cartridge’s base diameter. For the 45 ACP, the rim is .04″ larger than its base. For 45 LC, the rim is .32″ larger than the base diameter. So, what the author was trying to communicate was that you’re much more likely to notice the long colt’s rim as it protrudes out about 8x as much as the ACP’s. (We’ve updated the wording in the article as what we initially wrote was definitely not clear, sorry for the confusion.)
what does +P+ means
Hi James, thanks for asking! The short answer is that +P+ ammo is a load that’s pressure is about 18% higher than a standard load. If you’re looking for more details about +P and +P+ ammo, we have a longer article about it available here: https://www.ammoforsale.com/ammo-club/what-is-p-ammo/.
Though officially replaced in military service, those who are given their choice of sidearm like SEAL teams and other special forces units still prefer the 1911 in many cases. So the 1911 is actually still in use today by the US military. 110 years after it past it’s initial testing.
I was forced to replace my WWII era 1911 in 1996 going to a new 9mm. Qualifying with a pistol went from a joy with the 1911, to a nightmare with the 9mm. The 1911 was more accurate in general and suffered less difference in shot placement from pistol to pistol than the 9mm.
There is a reason the 1911 was and still is preferred over newer 9mm for military service, and it isn’t just the opinion of the soldier. The reliability and accuracy of the 1911 is amazing, and the stopping power of the .45 ACP is battle proven. John Moses Browning was a true genius in firearm design, and the 1911 was his masterpiece.
I still carry a 1911A1. Everyone thinks they need 13 or more rounds for self defense. If you need more than 2 against one person. Your a bad shot. And most likely will kill people behind them. I also own a Glock 36. Good pistol chambered in .45 Cal. With a 6 round + one magazine. A friend of mine carry’s a Glock 19 in a Miami Vice(old TV show)type holster with two mag holders under his right arm. So he has 46 rounds at his deposal. Who needs that? Outside of service I have pulled my weapon out 3 times over 35 years. And only fired one round. The first was killing(the one shot)a Rabid Racoon. The second was a man with a knife(he gave up). The third was a man in my fenced back yard looking into our windows(a stupid insurance adjuster who let himself in). My point being in war if you have to resort to using a handgun. The .45 1911A1 is the way to go. Since you cannot use Hollow point bullets. It has more stopping power than a 9mm. The change is under way. At least for Military Police and some special units.
Why can’t you use hollow points? For that matter, why can’t hunting rounds be used in combat?
Lol, spot the fudd
FOLKS I HAVE A SINGLE SHOT TAURUS TARGET PISTOL THAT ACCEPTS .410/.45 LC AMMO. MY QUESTION IS CAN I SAFELY USE .45 ACP AMMO IN THIS PISTOL FOR SELF DEFENSE? I’M OBVOUSLY A LOST BALL IN HIGH WEEDS WHEN IT COMES TO FIRE ARMS BUT I WOULD LIKE TO DEFEND MY HOME IF NEED BE. PLEASE HELP ME.
Hi Jerry –
45 ACP and 45 Long Colt ammo are not interchangeable. Even if you somehow get the cartridge to fit, I would not recommend putting the 45 ACP ammo into the chamber of your 45 LC pistol — it could lead to a big boom that is more likely to hurt you than a potential attacker. (Sorry, I know this isn’t the answer you want to hear but I don’t want you to get hurt.)
I disagree. They are not interchangeable physically. If you could gerryrig it,it would not blow up the gun. They make revolvers with interchangeable cylinders so that they can fire both cartridges. The specs on both are very close.
HOWEVER, there’s one thing that will blow up your gun. And that is loading a .44 magnum into a .45 Colt. And yes they will fit. A Ruger Blackhawk might survive, but I doubt any others would. Don’t mix cartridge’s.
Taurus is supposed to be designing moon clips for the Taurus as S&W did for the Governor. The Governor uses the moon clips to hold the 45 ACP and keep the rounds from slipping into the cylinder.
Love my 1911 hated the M9 most veterans agree with me
The M9 Was a piece of junk.
So much dising the Beretta 92 and its kids.. fun fact the 92 was the MOST accurate semi-auto handgun tested back in it’s day. Maybe crappy worn sloppy Beretta’s are what you shot? I can still remember the ex Masad writers words “The 92 FS is the first factory pistol I have ever shot that maintained 2″ or smaller groups with all ammo tested”
Will the 92 fit small hands…nope…great double action…nope….reliable…yup….accurate…very
My issue was always the slide mounted safety. It’s not an issue shooting your quals, but I discovered I had a real issue hiring the decocker/safety during a few more dynamic courses I artended during various predeployment training.
They could have just done like the Taurus pt92 and moved it onto the frame. Oh well. 1911’s are obsolete. 124gr 9mm NATO actually produces higher muzzle energy than .45 acp, all while shooting flatter, offering more reliable expansion and penetration, reduced felt recoil and muzzle flash, and offering 2-3x the number of rounds in a full sized combat pistol.
9mm is better in almost every scenario than .40 s&w and .45 acp. Just look to practically all professionals who actually rely on pistols. It’s almost all 9mm.
Iam sorry for all of you gun ***. (Prior marine profanity is key) but u nut jobs thinking 1 more round is better than 6… ?
Sounds like you need shooting lessons or you need to be shot at. Solid question of mine is the cowboy action magnum round more powerful than a standard .45 acp.
Who cares about the xra round. Make me feel i need to return to my brothers instead of you 20yr old dipshits who don’t know what the fuc im talking about. Website is great for kids old enought to by a gun.😚
Sounds like YOU need ENGLISH lessons.
Ok, so the .45 Colt or Long Colt and the .45 ACP are Not interchangeables.
That’s correct Orlando – you should not use these interchangeably and using 45 ACP in a 45 LC firearm could possibly result in malfunction or serious injury.
They need to add to the content of their page. The S&W governor can shoot both and it’s a revolver.
Yep, you’re right Michael. The Governor can accept both cartridges (along with .410 too.)
https://www.smith-wesson.com/product/governor?sku=162410
People need to know the appropriate ammo to use and not depend on posts. If not, put the weapon down and get some training.
Definitely agree that training is worthwhile James. (Often, when we get in weird ammo markets, people are desperate to find ammo they can safely fire. That’s where questions about 45 Long Colt versus 45 ACP often come up.)
You can shoot .45acp rounds through a .45 LC if you clip them into a retaining star clip. Kind of a pain but .45acp much easier to find and cheaper.