The .45 ACP Cartridge

.45 ACP cartridge
The famous .45 ACP cartridge.

When you take a look at the large missile-shaped cartridge of your average deer rifle, and better yet, when you put the rifle to your shoulder and fire it, a little alarm ought to go off in your head about pistol cartridges–all pistol cartridges. They are all inadequate in terms of real power. I like Clint Smith’s definition that “a pistol is something you use to fight your way back to your gun.” Pistols have their place due to the ease with which they can be carried and brought into action, but it’s important to recognize their limitations. Notice that no fighting force in history has gone into battle armed with pistols as their primary weapons.

Some pistol cartridges are less inadequate than others, and one which comes pretty close to adequate is the .45 ACP. “ACP” stands for “Automatic Colt Pistol.”

John Browning is credited with having designed the .45 ACP cartridge. Browning’s .45 ACP ammo was built specifically for the pistol that many of us regard as one of the greatest pistol designs ever, the M1911. However, I’m not at all sure that the M1911 wouldn’t have been chambered for .38 Super had Browning been left to his own devices.

The man who pushed the Army into adopting the .45 caliber cartridge was Gen. John T. Thompson, the father of the Thompson submachine gun and a member of the Army Ordnance Board during the time that the M1911 pistol was being developed by John Browning and Colt. After the disastrous showing of the Army’s .38 Long Colt pistols in the Philippines, Gen. Thompson was committed to the idea that the Army should be packing a real man-stopper in its handguns, a big .45 caliber bullet.

It was the cartridge tests conducted by Thompson and Major Louis Anatole LaGarde of the Medical Corps in 1904 at the Nelson Morris Company Union Stockyards in Chicago that resulted in the adoption of the .45 caliber as the official U.S. Army handgun cartridge. They tested various calibers on live cattle, deer, and human cadavers to determine the best load. From these tests it was determined that the .45 was the most effective cartridge for a handgun, but with reservations. In their report, they state:

“the Board was of the opinion that a bullet, which will have the shock effect and stopping effect at short ranges necessary for a military pistol or revolver, should have a caliber not less than .45”. But they also said, “…soldiers armed with pistols or revolvers should be drilled unremittingly in the accuracy of fire” because most of the human body offered “no hope of stopping an adversary by shock or other immediate results when hit.”

In response to the Ordnance Board’s specification, Browning designed the .45 ACP for the pistol he was submitting to the board. Browning’s first loading was a 200 grain bullet running at 900 feet per second, but the Army wanted a larger bullet. Browning responded with the loading we have today, a 230 grain bullet with a muzzle velocity of 830 feet per second.

Stopping Power

It is interesting to observe that we are still arguing this basic question of terminal ballistics which was articulated by Thompson in 1904. The tag-team wrestling match in the terminal ballistics field is currently between Ed Sanow and Evan Marshall in the “small and fast” corner, and Dr. Martin Fackler (backed up by Thompson and LaGarde) in the “big and slow” corner. This discussion quickly degenerates into a lot of arcane mumbles about temporary and permanent crush cavities, energy transfer, hydrostatic shock, and the Miami FBI shoot-out. It’s interesting if you’re a physicist or a forensic pathologist, but it gets kind of academic for the rest of us. “Small and fast” works really well with high-powered rifles when their small 80 grain bullets are traveling at 4000 feet per second, but hand gun cartridges don’t operate at those energy levels. The best of the small and fast pistol rounds is the 125 grain .357 Magnum which has enjoyed an impressive service record in the “one shot stop” statistics. It has also suffered some spectacular failures in which the bad guy was shot multiple times center of mass and remained on his feet.

Evan Marshall and Ed Sanow have worked up a set of statistics based on results of actual shootings in which one shot was fired into the torso of the attacker stopping the assault, and from these studies they have developed percentage ratings for “one shot stops” for cartridges from .22 to 12 gauge. The Marshall and Sanow numbers show a tendency for small and fast cartridges to do somewhat better than large and slow ones, i.e., .380’s do slightly better than .38 Specials from 2″ barrels and .357 Magnums do a percentage or so better than the .45 ACP. Understand that controversy still rages about the Marshall and Sanow study, particularly about their methods, sources of data, and the shootings they chose to exclude. Nevertheless, it’s an interesting study.

Jim Higginbotham, a 30-year law enforcement veteran and trainer writes the following on the subject of pistol cartridges and failures to stop:

While I have come across some lethal encounters that took a lot of rounds to settle they mostly were the result of either poor hits (or complete misses) or lack of penetration. Nearly all of the high round count cases I have reviewed involved 9mms, .38s, .357’s or smaller calibers. This is not to say they do not occur with major caliber rounds. It is to say I have been collecting data for 30 years and have not encountered many cases in which multiple hits (more than three as two or three shots are a fairly normal reflex action) from major caliber cartridges to the center of the chest have not been sufficient, – the single exception being a case involving the .41 Magnum loaded with JSP bullets which did not expand – they did penetrate – it took five hits center mass to stop the attacker – and I have not encountered any with the .45, even with Ball. I have encountered several with 5, 6 or even more hits to the center of the chest with .38, .357, 9mm and .223 rifle rounds failing to stop. Almost every one could be traced to lack of penetration with a couple of exceptions that hit the heart but just did not cause enough damage to be effective quickly. Note I am not talking about “torso” hits. There is a lot of area in the torso in which a hit will seldom produce rapid incapacitation even if hit by a 12 ga. slug or a 30-06 – we simply cannot count such data if we are going to learn anything.

My purpose here is not to argue Fackler versus Marshall and Sanow because that’s a book in itself. What is important in all of this is that regardless of which philosophy you choose to accept as true, the .45 ACP comes out well–at or near the top of the effectiveness ratings for both schools of thought.

Having established the almost universal agreement that the .45 ACP is an acceptable personal defense cartridge (kind of like proving the ocean is wet), are there negatives? Sure there are. For one thing, the .45 ACP is big and heavy. The same characteristic that makes it so admired by the big hole school also makes it heavy to carry and bulky, resulting in fewer rounds being available in compact handguns. A fully loaded Thompson submachine gun is fairly heavy if you have to lug it around through a hot jungle all day. Some people find the recoil of the .45 ACP punishing although I’m not one of them (I actually prefer the recoil of the .45 ACP over the recoil of the 9mm). The penetration of the .45 ACP 230-grain FMJ bullet is 26″ in ballistic gelatin, making it problematic and dangerous as a personal defense load. The threat of over-penetration with the military round necessitates the use of hollow points for LEO and civilian PDW applications. Some of the older 1911 pistols don’t like hollow point bullets very well and have to be throated and have their feed ramps polished for reliability. And last, there is the cost. The .45 ACP is expensive as pistol cartridges go, often $3-$4 per box more than 9mm or .38 Special.


The specs and behavior of this cartridge are central to its success. Even people who don’t like the 1911-pattern pistol often seek other systems to launch the .45 ACP and every major gun maker builds pistols around the cartridge. Smith and Wesson even builds a revolver for it.

Specifications of the original military loading of the .45 ACP

Dimensions Minimum Maximum
Overall Length 1.256″ 1.266″
Bullet Length .657″ .667″
Bullet Diameter .451″ .451″
Case Head .4718″ .4734
Case Mouth .4672″ .4732″ (.4730″ standard)
Case Length .892″ .898″

Bullet Weight 230 grain (14.9 grams)
Bullet Type FMJ
Ballistic Coefficient .195
Muzzle Velocity 830 feet per second
Energy at 25 yards 350 foot-pounds
Effective Range 100 yards
Mid-Range Trajectory 1.6 @ 50 yards

Exterior ballistics

Maximum range In pistol, 1,600 yards.
In submachine gun, 1,700 yards.
Pressure 4,000 pounds per square inch.
Velocity, Pistol @ 25.5 feet, 820 feet per second.
@ Muzzle, 825 feet per second.
Velocity, Submachine Gun @ 25.5 feet, 885 feet per second.
@ muzzle, 990 feet per second.
Muzzle energy 329 foot-pounds Ball, pistol.
383 foot-pounds in submachine gun.

Accuracy with muscle test
mean variations for several targets

Range Mean Radii
Yards Inches
25 0.86
50 1.36
75 2.24

Penetration in white pine

Range Depth
Yards Inches
25 6.0
100 5.5
250 4.0
The penetration in moist loam at 25 yards is about 10 inches. The penetration in dry sand at 25 yards is about 8 inches.

Table of fire

Range Time of flight Drop Deflection due
to drift1
Yards Seconds Inches Inches
10 0.037 0.3 0.1
20 .075 1.1 .2
30 .113 2.4 .3
40 .151 4.4 .4
60 .229 9.9 .8
80 .308 18 1.3
100 .388 28 2.0
1 Drift id to the left. Based on a velocity of 800 feet per second, 25 feet from muzzle.

One of the goals of my life to which I am committed to making a reality is to render all of this ballistic speculation academic by never having to shoot anybody. Much of my time with a handgun is spent doing fun stuff like target shooting and IDPA matches. The .45 is a fun gun and cartridge to shoot. It’s hard for me to imagine myself shooting a match with a DA/SA “crunchenticker” (as Col. Cooper likes to call them). I could if I had to, but I don’t have to so I don’t.

You often hear it said that the 1911-pattern .45 ACP is “an easy gun to shoot well.” Experience and the testimony of generations of shooters bears this out. Although this ease in doing well is generally attributed to the properties of the pistol, particularly the trigger, it’s my opinion that the .45 ACP cartridge contributes to the superlative performance of the handgun. The .45 ACP 230g FMJ is possessed of great inherent accuracy. With the excellent trigger and this load, you can shoot ragged holes all day.

Related Links

Background Information on the United States Pistol Caliber .45 M1911 – Development history of the M1911 .45 Caliber Automatic Pistol including the Thompson-LaGarde cadaver tests of 1904

.45 Auto Cartridge Development – Stefano Mattioli’s article on the early development of the .45 ACP cartridge. Includes specs and drawings of these early cartridges such as WRA 1904.

Comments, suggestions, contributions? Let me know