10mm vs 45 ACP: Which Auto Is Best?

In today’s market, fans of large-caliber pistols will eventually find themselves considering the 10mm vs .45 ACP, but which of these is really best for your needs? The .45 ACP has enjoyed a long tenure of being touted as America’s king of pistol cartridges, but is the newer 10mm Auto a better choice? That depends.

Like rifle shooters, pistol shooters can get pretty persnickety about the cartridges they prefer. Some of those preferences are based on experience and sound reasoning, others aren’t. You might encounter drill-sergeant-like blowhards at the local shooting range—or internet forum—who say things like: 

• I shoot a .45 ACP, because they don’t make a .46!
• Do not attend a gunfight with a handgun, the caliber of which does not start with a “.4”
• I shoot a .45 ACP because shooting twice is silly.

These aren’t the people you should seek advice from if you’re wanting informed opinions. Large-caliber autos offer advantages and suffer from disadvantages too. If you can navigate the machismo and misinformation, choosing the right caliber for you becomes pretty simple. If you’re considering 10mm vs .45 ACP, here’s what you need to know. 

Knee-Jerk Cartridges

Both the .45 ACP and 10mm Auto were developed in response to unsatisfactory outcomes with smaller pistol cartridges during specific events. They both were arguably born of a knee-jerk desire or perceived need for a more powerful pistol cartridge.

Origin of the .45 ACP

The .45 Automatic Colt Pistol (ACP) was famously designed by John Browning in 1904, and eventually adopted in 1911 by the U.S. military in his Colt auto, which we know as the model 1911.  In the Philippine-American War, which began in 1899, U.S. soldiers apparently had trouble stopping indigenous warriors with their .38 Long Colt revolvers. The .38 Long Colt fired 148- and 150-grain bullets at around 750 feet per second, and was less powerful than the 9mm Parabellum, which was designed around this same time, in 1901. The dismal results attributed to the .38 Long Colt spurred the development of a new service pistol cartridge that was requested to be at least .45 Caliber. John Browning already had developed a couple of smaller autoloading cartridges for his pistols, and set about designing a .45 caliber round to meet this need. Thus, the .45 ACP was born.

Birth and Rebirth of the 10mm Auto

Like the .45 ACP, the 10mm Auto was an answer to the perceived problem of power-deficient handguns. The tragic 1986 FBI shootout in Miami spurred the bureau to seek out a more authoritative semi-automatic service cartridge. The shootout involved 8 FBI agents armed with a couple shotguns and 9mm, .357 Mag., and .38 Special handguns. Analysis of the events led the FBI to partially blame a lack of “stopping power” in its handgun cartridges, as well as the disadvantages of revolvers for the outcome. The answer to these shortcomings was the 10mm Auto. 

The FBI’s adoption of the 10mm Auto was short lived. They found that the sharp recoil of the cartridge, along with the large-framed handguns, made it much more difficult for agents to shoot accurately and succeed in marksmanship qualification on the range. They first used lower-velocity “FBI Lite” 10mm loads, then moved to adopt a shortened version, the .40 Smith & Wesson that matched those lower-powered ballistics. For decades, only a handful of 10mm pistols were available: 1911s like the Colt Delta Elite, and one polymer pistol, the Glock G20. More recently, the 10mm Auto has seen a resurgence, becoming popular for backcountry defense against bears. Amid this comeback, it’s become more popular than ever before, and most manufacturers now offer flagship pistols chambered in the powerful cartridge. The 10mm Auto is now popular in both 1911-style and double-stack polymer pistols, like this Taylor’s & Company Tactical 1911 pictured below.

Taylor's & Company Tactical 1911

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10mm vs .45 ACP: Specs and Design

The basic anatomy and construction of most semi-automatic pistol cartridges are very similar. Both the 10mm Auto and .45 ACP employ straight-walled cases without a protruding rim, and both headspace off the case mouth. 

The most visibly different design characteristics between the two cartridges are the projectile shape and the shape of the extracting groove. The .45 ACP typically employs a rounded-nose projectile, while the 10mm often uses a truncated-cone, flat-point bullet—at least with ball ammunition. The extracting groove of the .45 ACP—the groove in which the extractor hooks the rim of the case—has a 26-degree angle up to the body of the case. It looks very similar to other Colt auto cases like the .32 and .380 ACP. The 10mm has a shorter, 45-degree ramp from the bottom of the extracting groove to the case body. If you need further education on this, mix up a 5-gallon bucket of .45 ACP and 10mm auto brass, then sort them out. You’ll be an expert in no time. 

.45 ACP Specs

• Bullet Diameter: .451 inches
• Max Cartridge Overall Length: 1.275 inches
• Case Length: .893 inches
• Bullet Weights: 135 to 230 grains
• Velocity range: 800 to 1,240 feet per second
• Year Developed: 1905 (Adopted in 1911)

10mm Auto Specs

• Bullet Diameter: .400 inches
• Max Cartridge Overall Length: 1.260 inches
• Case Length: .987 inches
• Bullet Weights: 115 to 220 grains
• Velocity range: 1,050 to 1,600 feet per second
• Year Developed: 1986 

Ballistic Battle: 10mm vs .45 ACP

When discussing the ballistic properties of any cartridge, we typically focus on bullet mass, velocity, and kinetic energy. Kinetic energy at the muzzle (or muzzle energy) is a valuable metric to examine, but remember that it doesn’t tell all. When taking account of the muzzle energy of Federal Premium’s .45 ACP 230-grain HST defensive load, we might think that 404 foot-pounds of energy seems pretty powerful. But when you consider that an average 62-grain 5.56mm or .223 load has around 1,200 foot-pounds of energy, the handgun doesn’t seem so impressive. 

Ballistic Properties of the .45 ACP

The .45 ACP is most widely used with 230-grain bullets. In its decades of military applications in the 1911 platform, that’s with ball ammo. The cartridge employs a wide, .451-inch-diameter projectile. It’s fired slightly faster than the defamed .38 Long Colt launched its 148-150-grain bullets. Bullet weights typically range between 185- and 230-grains, with 800 to 900 fps velocity. Here are some representative .45 ACP loads:

Ballistic Properties of the 10mm Auto

Similar to the .45 ACP, the 10mm Auto typically uses projectiles in the 180- to 200-grain range. However, it’s not uncommon to see bullets ranging from 115 grains to 220 grains. The 10mm cartridge is designed to operate at 37,000 PSI (SAAMI), while the .45 ACP tops out at 21,000 PSI (SAAMI). The smaller diameter .400-inch bullets leave the muzzle significantly faster than .45 ACP loads using similar-weight bullets and, consequently, the 10mm Auto has more kinetic energy. Here are some good examples of 10mm loads:

Head to Head: 10mm vs 45 ACP

What we’ve covered so far are just numbers on paper. Examining the differences between the 10mm and .45 ACP in a practical sense is more complex. Both cartridges are the result of a real or perceived need for more power, but the truth is that pure muzzle energy isn’t nearly as pivotal a characteristic as we might think—especially when comparing handgun cartridges. Even if a pure comparison of ball ammunition gives these more powerful cartridges an advantage, it’s far from being the universally deciding factor on which is best.

Muzzle Energy Isn’t the Biggest Factor

When discussing the stopping power of a handgun cartridge, remember that neither the 10mm Auto or .45 ACP has a decisive amount of kinetic energy. Relatively, the .45 ACP has only about 70 percent of the energy of the 10mm Auto, but both cartridges only have about a third of the energy that the meager .30/30 Winchester and .30/40 Krag—which was also blamed for insufficient stopping power in the Philippine war.

All else equal, using ball ammunition, there’s no doubt that the larger, wider .45 ACP is a harder-hitting cartridge than the .38 Long Colt or the 9mm. The relatively low velocity and kinetic energy simply can’t compare to that of a rifle cartridge, and results surely varied. The machismo quotes about the .45 ACP only requiring one shot to eliminate a threat are bunk.

Similarly, the killing or stopping power of the 10mm Auto must be considered in context. It too has relatively low kinetic energy compared to rifles. The increased velocity and better sectional density of the 10mm bullets give it an advantage in penetration of hard barriers, especially with cast or solid projectiles. Even as the 10mm is contemporarily lauded for bear defense applications, we have to acknowledge that kinetic energy isn’t the primary mechanism for stopping a bear. It’s simply not enough. Take a real bear-stopper for instance, the .375 Ruger. A pet load of mine shooting 270-grain Lehigh Defense Controlled Fracturing bullets boasts 4,870 foot pounds of kinetic energy. This load exists in an entirely different universe than either the .45 ACP or the 10mm Auto.

Terminal Performance

For personal defense applications, modern projectiles have somewhat leveled the playing field of terminal performance of handgun cartridges. In the case of 10mm vs 45 ACP, quality expanding defensive bullets have effectively standardized the amount of acceptable penetration, based on FBI criteria. Shooting editor John Snow published a story a few years ago examining this between the 9mm and .45 ACP. 

The 10mm certainly has a measurable advantage over the .45 ACP in terminal performance, due to its velocity and sectional density, but quality defensive ammunition will limit the cartridge’s penetration to about the same depth as similar ammunition fired from a .45. The wider diameter of the .45 ACP bullet, and the speed of the 10mm bullet effectively nullify each other when it comes to wound cavity characteristics. To summarize, the 10mm has an advantage, but not a very big one. 

When using solid cast or other monolithic, non-expanding bullets, the 10mm has a clear edge in penetration over the slower, fatter .45 ACP. Though loads like the Underwood Extreme Defender 135-grain monolithic increase the efficacy of the .45, they’re still out-shined by 10mm ammo loads like the Black Hills Honeybadger, which fires a 115-grain monolithic at nearly 1,600 feet per second, producing a wound cavity similar to a 240-grain JHP fired from a .44 Magnum (which you can see in the ballistic gel below). The Buffalo Bore Outdoorsman 220-grain hard cast load is another that the .45 ACP simply cannot keep up with.

Capacity

Die-hard fans of the .45 ACP often tout the 1911 as the best combat handgun ever, and the pistol has the clout to back that up. A pistol design doesn’t stay in service through four major wars and 74 years by being a shitty gun. It has proven itself time and again. During much of the 20th century, many service pistols had limited capacity. The Luger, Walther P38, or VIS P35 9mm pistols, had 8-round magazines. The 1911 also had an 8-round mag, but loaded with the more powerful .45 ACP, it had the advantage. We now recognize magazine capacity as a valid metric when considering a pistol cartridge. 

Normally, a higher-powered pistol cartridge will be larger and result in lower ammunition capacity. That’s not the case in the 10mm vs .45 ACP consideration. The smaller diameter 10mm cartridge is both more powerful and allows greater magazine capacity in most handguns. Many 10mm Auto and .45 ACP pistols use the same frame, and their grip size is often the same too. Many 1911-style 10mm pistols have either 8- or 9-round magazine capacity, similar to the .45 ACP. However, in popular polymer pistols, the 10mm guns can usually squeeze 15 rounds into the magazine as opposed to 13 rounds of .45 ACP.

Shootability and Recoil

One of the biggest advantages of smaller pistol cartridges like the 9mm, considering the advancement of bullet technology and quality, is its softer felt recoil. Softer recoil allows a shooter to recover more quickly and get the next shot on target more accurately. This advantage favors the .45 ACP when compared to the 10mm Auto. 

The least appealing characteristic of the 10mm Auto is it’s relatively sharp, snappy recoil. It can certainly be managed, but relative to the .45 ACP, the 10mm is at a disadvantage—in the same way large revolvers like the .44 Magnum are at a disadvantage compared to the 10mm Auto in a bear defense application. Shootability matters. 

The .45 ACP is not considered a soft shooter, but generally, recoil is slower and softer than that of any comparable 10mm Auto. In the case of well-tuned 1911 pistols like the ones from Wilson Combat, Gunsite, and Nighthawk Custom we tested at our 2023 1911 test, the .45 can be run nearly as quickly and accurately as a 9mm. Though the 10mm can be mastered, the shootability of the .45 ACP could conceivably make up for its disadvantage in capacity—especially in normal self-defense applications.

10mm vs .45 ACP Through a Suppressor

Suppressors are more popular than ever, and if there were one pistol cartridge made for shooting through a suppressor, it’s the .45 ACP. Because nearly all .45 ACP loads are subsonic, they’re inherently quiet when shot through a can. There’s no supersonic crack, and the lower pressures of the cartridge make the supersonic expanding gasses easier to contain. 

The 10mm isn’t so lovely when paired with a suppressor—at least in my experience. The supersonic .40 caliber bullet produces a louder report due to the sonic crack of the projectile. You can load heavier bullets at subsonic levels, but I’ve experienced strange things when shooting through my Silencerco Hybrid 46 suppressor. Through both a Glock G20 and FN 510 Tactical, I experience endcap strikes, with the bullet barely grazing the top edge of the appropriately-sized endcap hole. I have no problems when using a .46-caliber endcap, but the report is louder. I’m not sure what’s causing it, but the bullets appear to be stable, cutting clean holes in paper when not using the suppressor. If you want to use a silencer, go with the .45 ACP.   

Read Next: 9mm vs 10mm

FAQ

What is the velocity of a 10mm round compared to a .45 ACP?

When using equal bullet weights, the 10mm Auto is usually 200 to 300 feet per second faster than the .45 ACP.

Which has more recoil: 10mm or 45 ACP?

The 10mm Auto generally has harder, snappier recoil than the .45 ACP.

Can the .45 ACP stop a bear?

With purpose-built, monolithic bullets, the .45 ACP is capable of stopping a bear, but the 10mm is better-suited for the task.

Is 10mm or .45 ACP better for self defense?

Both are great self-defense cartridges, but the softer recoil of the .45 ACP gives it an advantage. If you’re also concerned with wildlife defense, the 10mm is better to cover both applications.

Final Thoughts

Though I don’t believe that simply using a larger bullet, or having more power would have changed the story for our troops at the turn of the 20th century, or abbreviated the bloody fight with a couple of bank robbers in Miami, we are better off having both the 10mm Auto and .45 ACP cartridges. 

Which is best? Like I said, it depends. Generally, the .45 ACP is a better option for those concerned with self defense. It’s also a more enjoyable cartridge for a target shooter. The 10mm has a distinct advantage for those who want a dedicated backcountry defensive handgun. Compact versions make great crossover EDC pistols that you can carry with confidence in the backcountry.