Few firearms have captured a nation’s spirit quite like John Moses Browning’s vaunted M1911. Rugged, reliable, cleverly engineered, and utterly lethal, this homegrown handgun is as American as baseball and blue jeans.
Yet, what would the legendary 1911 be without the potent and equally loved .45 ACP cartridge that Browning designed to go with it?
Even though it’s dubbed “the Lord’s caliber” thanks to its widespread popularity – and dare I say, righteous stopping power – I feel we’ve come to take the .45 ACP a bit for granted these days. Here’s a closer look at the story behind a pistol cartridge that helped define American small arms for over a century.
Table of Contents
.45 ACP History
Basic Ballistics & Specs
Pros & Cons
Final Thoughts
.45 ACP History
Developed in 1904, the story behind the .45 Automatic Colt Pistol (commonly .45 Auto and .45 ACP) is tied directly to America’s rise to prominence on the world stage. While the genius of the cartridge came squarely from the mind of Browning, it was actually the U.S. Army that determined the need for a .45-caliber bullet.
This owed much to two factors. First, America’s cavalry at the turn of the 19th century was on the hunt for something to replace the aging Colt Single Action Army revolvers chambered for the rimmed .45 Long Colt.
Meanwhile, a pressing second factor emerged from battlefield experiences during the Philippine-American War (1899-1902) and the Moro Rebellion (1902-1913) in the Philippines. American troops reported poor performance from their smaller .38-caliber revolvers during the campaign.
Frontline reports rolled in, describing harrowing hand-to-hand encounters with enemy fighters who simply shrugged off multiple hits from the U.S. Army’s rimmed .38 Long Colt, which was only recently adopted in 1892. This kicked off a hunt for something new and more powerful.
From the extensive Thompson-La Garde ballistic report in 1904, the army concluded its findings with the following determination: “After mature deliberation, the Board finds that a bullet which will have the shock effect and stopping power at short ranges necessary for a military pistol or revolver should have a caliber not less than 0.45.”
So, the stage was set, and the U.S. Army wanted a .45 caliber projectile similar to the .45 Long Colt already in use with the cavalry. It did not, however, want to return to a slow single-action-only revolver after its intense close-combat experiences in the Philippines.
At the time, Browning and Colt were already working on a .41-caliber prototype cartridge to go with a new semi-automatic pistol design from Browning. They responded to the new request for a .45-caliber cartridge by essentially redeveloping Browning’s handgun design and .41-caliber cartridge. This led to the Colt 1905, which was the first handgun chambered for the new .45 ACP.
Later U.S. Army trials led to the adoption of both Browning’s .45 ACP cartridge and 1911 pistol. Thus, one of the world’s most iconic caliber-gun duos of all time was born. The M1911 chambered for .45 ACP went on to become America’s longest-serving military handgun.
Its military record from 1911 until the mid-1980s made it a household name. But its performance on and off the battlefield made it a legend.
Basic Ballistics & Specs
Like the British .455 Webley, the .45 ACP was a straight-wall design that leaned heavily on the sheer mass of the bullet over velocity to do much of the downrange damage. Unlike the rimmed Webley casing and Browning’s earlier semi-rimmed .32 ACP, the new .45 ACP was a truly rimless cartridge.
Both the straight wall and rimless profile were meant to help the .45 ACP function specifically inside semi-auto firearms that fed from magazines instead of cylinders. At first, the Colt 1905 was tested with 200-grain bullets, but this was increased to 230 grains for what became the standard .45 ACP.
Before we dig into muzzle velocities and other data points, it’s worth highlighting that the U.S. military was very, very interested in terminal performance over simply specs. To that end, the Thompson-La Garde Tests from 1904 took a rather gruesome turn with testing on live animals.
This included a head-to-head comparison of the effects of close-range fire on living cattle with a .45-caliber projectile and a rising star in the 9mm Luger. Here are two brief but graphic excerpts of the results:
Blunt .45 Caliber: “9:46:30 A.M. Animal shot through lungs from left to right; fell to the floor at the sixth shot. Hemorrhage was free from one of the perforations in the right side. The animal was very much excited and kept jumping from side to side until she fell to the floor. Death occurred at 9:49 A.M.”
9mm Luger: “10:15 A.M. Animal was shot from left to right. There was an interval of one minute between the second and third shots, due to a hitch in the working of the pistol.
At 10:18:15 A.M., when the animal had been shot eight times, there was a short interval on account of reloading the magazine. Two shots were fired through the abdomen; at this time the animal was bleeding from the mouth.
After twelve shots had been fired the cow was still standing and had to be killed by the hammer. Ten shots were fired through the lungs and two through the abdomen in this experiment.”
As gruesome as the testing was, the clear impression left on the U.S. military was that the hefty .45 delivered with its heavy weight what the 9mm couldn’t with higher velocities. That terminal performance is still largely represented in the basic ballistics of modern 9mm and .45 ACP ammunition.
Here’s a quick comparison of basic, 124-grain 9mm FMJ and 230-grain .45 ACP FMJ.
You can also compare the .45 ACP stats from above to the rather anemic black-powder 150-grain .38 Long Colt, which offered velocities ranging from 650 to 750 fps. That put it at a mere 140 to 187 foot-pounds of energy. Even the switch to modern smokeless powder only bumped velocities to 750-800 fps. That left it at a relatively low 187-213 foot-pounds of energy.
For the modern shooter, there’s another benefit to the .45 ACP’s slower velocity. The increasing popularity of suppressors benefits from the subsonic speeds generated by the .45 ACP. Normal muzzle velocities for the .45 ACP generally fall between 800 and 900 fps, staying well below the speed of sound (1,125 fps at sea level in 68 degrees Fahrenheit).
Since this slow-flying bullet has enough mass to make up for its velocity, there’s a good reason .45 ACP is a popular suppressor round for handguns and pistol-caliber carbines. This quality was well known to gun designers in the 20th century, with firearms like the integrally suppressed British De Lisle commando carbine using the slow-moving .45 ACP as a quiet sentry killer in World War II.
Pros & Cons
Here are my top five pros and cons for the iconic .45 ACP. Keep in mind that modern specialty loads can vary greatly, so these are only based on the most general characteristics of the cartridge.
Pros:
- Strong terminal ballistics due to heavy weight
- Suppressor-friendly velocities
- Reliable semi-auto design
- Common and easily found caliber
- Over 100 years of proven performance
Cons:
- Large size lowers magazine capacities
- More expensive than 9mm
- Low velocities for longer ranges
- Usually more recoil than calibers like 9mm
- Heavier overall weights for carrying
Final Thoughts
The sheer number of 1911-type firearms still in production, with new variants arriving every year, is a solid testament to just how much America is still in love with Browning’s design. The .45 ACP remains a part of that legacy.
I have no doubt the caliber debate will continue to rage well beyond even the modern era’s “9mm vs. everyone else” trend. As for the classic .45 ACP, I can’t imagine it leaving the American marketplace in my lifetime. Anything is possible, but I think there are too many shooters who love the round for its history and performance to let it just fade away.
In fact, it’s still well-respected for its terminal performance and suppressor-friendly qualities. That has kept it as a go-to option for many law enforcement groups and private citizens. It’s also still a common feature inside Special Operations arsenals, even if its general military use has largely waned.
The “Lord’s caliber” gets the job done.
The Battle of Caloocan was one of the opening engagements of the Philippine–American War, and was fought between an American force under the command of Arthur MacArthur Jr. and Filipino defenders led by Antonio Luna in February 1899.
American troops launched a successful attack on the Filipino-held settlement of Caloocan on February 10, which was part of an offensive planned by MacArthur Jr. Occurring a few days after an American victory near Manila on February 4–5, the engagement once again demonstrated the military superiority that American forces held over the Philippine Revolutionary Army.
However, it was not the decisive strike that MacArthur had hoped for, and the war continued for another three years.
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