The .45 ACP (Automatic Colt Pistol) was forged in battle. In the late 19th century, the U.S. Army was looking for a round to replace their .38 caliber cartridges. The American forces needed something with more stopping power than their standard issue, and Colt answered the call. The .45 ACP was designed by smithing legend John Browning in 1904, and it was adopted in 1910 by the U.S. forces, who also adopted the Colt Model 1911 firearm at the time as an official addition to the military arsenal, designated M1911. Below we’ll cover all of the important points of this hugely important bullet in our Definitive .45 ACP Ammo Guide.

.45 ACP Explained

What Does ACP Stand for? What Does .45 ACP Mean?

.45 ACP

Automatic Colt Pistol was the name given to the series of cartridges designed by John Browning at the beginning of the 19th century. There are five ACP cartridges, the largest of which is the .45 caliber.

A History of the .45 ACP: Invention, Original Use, Adaption

The Philippine-American War (1899-1902) proved that there simply was not enough power behind the bullets which were fired at the time. After the war was over, the U.S. Army’s Generals went shopping for a new kind of cartridge, one which would be powerful enough to neutralize human targets on impact, but small enough to be carried by the common infantry and cavalry troops.

John Browning, Father of the .45 ACP

Browning and Colt were experimenting with various pistol calibers at the time, so when the U.S. Army and Cavalry asked Colt to submit a design for a bullet in a .45 caliber, Colt modified its .41 pistol – which was still in its prototype phase – and moved on to bigger and better things with the .45 caliber. The result of this was the .45 ACP cartridge, which Colt submitted for inspection to the military in 1906.

The new round blew the competition away, and after a series of tests and trials it was announced as the winner. After several more modifications were made, at the behest of the U.S. Army, the new and advanced “Cal. .45 Automatic Pistol Ball Cartridge, Model of 1911” was adopted by the military. The M1911 was produced until 1970, and only in 1986 was the Beretta M9 (9mm) brought in to replace it as the standard U.S. sidearm. That is one hell of a long run, and it goes to show how effective the .45 ACP bullet is in combat.

.45 ACP Cartridge Explained

.45 ACP Ammunition

The .45 bullet (11X23mm) is a round which is accurate and deadly. It comes in relatively heavy loads, due to its size. This is an advantage to some, and a disadvantages to others. It depends on the intended use, really. The .45 ACP comes in a wide range of weight and performance levels, so there is a lot to work around. It’s not a cur and dry kind of situation. The .45 caliber was used for decades by the military, and for good reason. While it may not be as fast as a 9mm bullet, it hits with a much greater punch.

.45 ACP Ballistics Performance Overview

Here is a quick rundown of the ballistic properties of the .45 ACP round, in various grain sizes and casings (source: Wikipedia).

Bullet Weight / TypeVelocityEnergy
185 grain / Bonded Defense1,225 feet per second835 Joules
185 grain / Jacketed Hollow Point1,050 feet per second614 Joules
200 grain / Jacketed Hollow Point +Pressurized1,080 feet per second702 Joules
230 grain / Federal Hydra-Shok900 feet per second561 Joules
230 grain / US Army Ball Full Metal Jacket830 feet per second477 Joules

Ballistics have a much greater effect when you are talking about military uses. In civilian uses, most armed confrontations occur within a distance of 5-10 yards. Within those short ranges, the ballistics don’t make that big of a difference. Ballistics are all about a projectile’s speed, mass, and force. When you are talking about the .45 ACP, you can see that the larger loads are inherently slower, but the bullet is nevertheless effective because of its sheer size.

.45 ACP Pros and Cons: Speed vs. Stopping Power

The energy and penetration capabilities of the .45 ACP round have made it a law-enforcement favorite, but along with the good comes the bad. The main drawback of the .45 ACP, especially when considering police and military use, is that its larger size and weight means that there is less speed and less firepower. I mean that literally – there is less room in a .45 caliber magazine. Many .45 ACP guns use single stack magazines, and even those who utilize a double-stack offer less rounds per mag, especially when compared to smaller calibers like the 9mm.

The .45 is also slower, as I mentioned, which could be detrimental in certain situations. However, consider that it was good enough for the U.S. Armed Forces for many decades – that says a lot.

Which Gun Companies Utilize the .45 ACP?

Many arms manufacturers still produce guns chambered in .45 ACP. Here is a partial list of some of them, and a few popular models.

Glock 21


  • Glock 21: semi-automatic, full size, striker fired.
  • Glock 30: semi-automatic, compact, short recoil, striker fired.
  • Glock 36: semi-automatic, subcompact, short recoil, striker fired.
Ruger SR1911


  • SR1911: semi-automatic, full size, short-recoil, single-action-only.
  • American Pistol 8615: semi-automatic, full size, striker fired.
  • SR45: semi-automatic, full size, striker fired.
Taurus PT1911


  • PT1911: semi-automatic, full size, short recoil, single-action only.
  • 24/7 G2: semi-automatic, compact, short recoil, double-action/single-action.
  • PT845: semi-automatic, full size, short-recoil, double-action/single-action.
SIG Sauer P220

SIG Sauer

  • P220: semi-automatic, full size, short recoil, double-action/single-action.
  • 1911 C3: semi-automatic, compact, short recoil, single-action-only.
  • P227: semi-automatic, full size, short recoil, double-action/single-action.
Springfield XD-45


  • XD-45: semi-automatic, full size, short recoil, striker fired.
  • GI45: semi-automatic, subcompact, short recoil, single-action-only.
  • Loaded 1911: semi-automatic, subcompact, short recoil, single-action-only.
Smith and Wesson M&P 45 Shield

Smith and Wesson

  • M&P 45 Shield: semi-automatic, full size, short recoil, striker fired.
  • SW1911 Compact: semi-automatic, compact, short recoil, single-action-only.
  • Governor: revolver, compact, single-action/double-action.

.45 ACP Matchups

Many times, a difference of several millimeters can have a huge impact on the power, speed, and penetration capabilities of a projectile. Engineers are continuously working to perfect handgun cartridges and make them more effective. How does the .45 ACP perform, compared to other popular calibers?

The Age Old Debate: .45 ACP vs .9mm vs .40 S&W

.45 ACP vs .9mm vs .40

These three cartridges are always being argued over. It is a constant, classic battle of power vs. speed. What are the differences between the three? Above all else, there is the actual difference in diameter. The .45 ACP measures 11mm, the .40 10mm, and the 9mm is – wait for it! – 9mm.

The .45 ACP is the biggest cartridge of the three. As such, you won’t get the same kind of magazine capacity as you would with the other two cartridges. The .45’s are larger, and they weigh more. It is a somewhat slower, yet highly effective projectile, which is why it was selected as the Army’s go-to combat bullet. The 9mm (referring here to the 9X19mm Parabellum) is one of the first cartridges for semi-automatic handguns. Light, effective, and accurate, it is the champion of 9mm-diameter bullets. It is significantly lighter than the .45 ACP, and it offers greater velocity than either the .40 or the .45 bullets. The .40 bullet is the most modern one of the three, having made its first appearance in the mid-1990’s. It is considered a middle point between the 9mm and .45 bullets. It is known to be heavier and slower than the 9mm, but lighter and faster than the .45 ACP.

With these three, it is always a question of intended use and/or personal preference. Some will not be fans of the .40’s recoil or loud report. Some won’t be fans of the .45’s lower magazine capacity. Some won’t be satisfied with the 9mm’s stopping power. It is a matter of speed and power, so every shooter has his or her personal idea on which is best. All three are great cartridges, and remember that the 9mm and .45 have been around for over a century – for good reason.

.45 ACP vs 10mm (Right)

.45 ACP vs 10mm

The 10mm (10X25mm) is considered more of an outdoor cartridge, for hunting and longer-range shooting, due to its flatter trajectory. It has a notable extra-loud report, which is a consideration when looking for a home-defense cartridge. Designed in the early 1980’s, it is still being produced today. Like the .45, it uses relatively heavier loads, starting at about 180 grain. 10mm ammo is generally more expensive, so that may also be a consideration for some.

.45 ACP vs .45 GAP (Left)

.45 ACP vs .45 G.A.P

The .45 GAP (Glock Automatic Pistol) is a shortened version of the .45 ACP. It has the same diameter as the .45 ACP, but has a shorter primer and a smaller build. It was introduced in 2003, along with the Glock 37 pistol. For a while, it made an attempt to compete with the .45 ACP. The maximum weight of the .45 GAP is 200 grain, which is significantly lower than that of the .45 ACP. Nowadays, only Glock manufactures pistols chambered in .45 GAP.

.45 ACP vs .380 ACP

.380 ACP

Browning’s ACP series consisted of five calibers, and of those five, the .45 and .380 are considered rimless cartridges. The .380 is a 9X17mm bullet, and as a 9mm round it retains some of the advantages of the aforementioned 9X19mm Parabellum round – lightness, speed, accuracy. Smaller loads of even less than 100 grain can reach high velocities and cause significant amounts of damage, especially at shorter ranges.

The .380 ACP round is famous for being used in the assassination of Archduke Franz Ferdinand before WWI, and it was a cartridge which was adopted by several nations as a standard, before the eruption of WWII. Compared with the .45 ACP, it has greater speed, less energy, and the capacity for greater firepower per mag.

.45 Colt

.45 ACP vs .45 Colt

The .45 Colt (also known as Long Colt) was designed in 1872, way before the .45 ACP ever hit the stage. It was adopted by the U.S. Army in 1873, and was the standard revolver cartridge for 14 years. It is a 11X33mm cartridge, and it is still being produced today, primarily for hunting purposes. The bullet diameter is the same as the ACP, but other than that it is a very different cartridge. The case, the guns which can fire it, and the round’s ballistics are all different.

.40 S&W

.45 ACP vs .40 S&W

The .40 S&W was developed as a law enforcement cartridge back in 1990. It is a 10X22mm cartridge, and when compared to the .45 ACP, the .40 S&W holds greater speed capabilities, but usually has greater recoil. The .45 ACP, on the other hand, has better penetration, and a much longer track record of over 100 years. .40 S&W cartridges are less expensive than .45 ACP.

.45 ACP Pricing

.45 ACP rounds will run approximately 30 – 35 cents per round (brass), and for reloads it will be about 17 – 20 cents per round. As always, ammo prices are manipulated and affected by politics, policies, and various ‘scares.’ .45 ACP cartridges are highly accessible, and they can be found online and offline in many locations. Like every other commodity, the price of ammunition rises and falls with the times. Keep your eyes wide, and you will be able to find a good deal somewhere.


As one of the oldest cartridges around, the .45 ACP is certainly holding its own. There is no doubt about it – John Browning was a genius. Many contemporary gunsmiths, weapons enthusiasts, and every day carriers owe a lot to the man who invented the .45 ACP round, among others. Even after all these years, it is considered a great round for self-defense and tactical situations alike. It might be heavier and larger than some of the other popular calibers, but it makes up for that with its sheer stopping power and quick follow up capabilities. At short ranges (which comprise the vast majority of all armed encounters), it is nothing short of deadly. Highly recommended, especially for those who find that 9mm simply isn’t cutting it.

Thanks for checking out our .45 guide. Be sure to check out some of our other features – like our Glock 30 and M16 reviews – here at Gunivore!

Nate M.

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