10mm and 45 ACP bullets

Comparing 10mm vs 45 ACP: Differences, Advantages, And Everything Else You Need To Know

Fans of big-bore pistols love comparing 10mm vs 45 ACP, since they are the most common big bullets for semi-auto pistols.

The short version is 10mm can be a bit more powerful than the .45 ACP if loaded that way and will usually have a slight magazine capacity advantage, but .45 ACP is cheaper and frankly is more capable than some people either know or want to admit! So...let's dig a little deeper.

10mm vs 45: is one better?

Some people just aren't satisfied with 9mm and want something bigger, and those folks usually wind up torn between 10mm vs 45 ACP. There are some more occult calibers out there, such as the large bore auto magnums and so on, but those are the most practical big bores.

Some folks end up wondering "which is best." Well...best for what? Best how? How do you define that?

Both are fine pistol cartridges, and suitable for almost any purpose you could have a pistol for. Some people also believe that both calibers have magical powers that they just don't!

So which should you get? Kind of depends on what you're doing with it. Let's talk about that a bit more.

Is 10mm Bigger Than .45?

45 ACP

10mm has a longer case than .45 ACP, but .45 ACP has a larger diameter. While this leads some people to believe 10mm holds more powder...that isn't actually the case.

With that said, here are the specifications:



.45 ACP

Bullet diameter

0.4 in

0.451 in

Case diameter

0.425 in

0.473 in

Case length

0.992 in

0.898 in

Overall length

1.26 in

1.275 in

Chamber pressure (SAAMI)

37,500 psi

21,000 psi

Case capacity (water grains)

24.1 grains

26.7 grains

So as you can see, 10mm has a longer case but a shorter overall length and a smaller projectile than .45 ACP. As you can also see, 10mm is loaded to a higher chamber pressure despite having less case capacity.

.45 ACP Because They Don't Make A .46

45 ACP bullets

By now we all know the story: John Moses Browning invented the .45 ACP (Automatic Colt Pistol) cartridge for what became the 1911 pistol because the US Army asked for it. They wanted a .45 Colt in a semi-auto, and that's what he gave 'em.

The standard .45 ACP load is a 230-grain round nose bullet propelled to about 830 feet per second (give or take) and about 350 foot-pounds (give or take) of energy. 185-grain and 200-grain bullets are the other common loadings.

What .45 ACP brings to the table is that it's a big, heavy bullet that can go in a semi-auto pistol, whereas .44 Special and .45 Colt are revolver cartridges. As far as big-bore cartridges go, it's relatively easy to shoot.

As far as terminal ballistics, .45 ACP is not the man-stopper that some believe. While the mass of the bullet favors greater penetration than 9mm and does make a bigger hole, the difference in terms of test performance (ie calibrated ballistic gelatin) and real-world performance with quality hollow points is rarely better than marginal.

Trauma surgeons cannot tell the difference between a 9mm wound and a .45 wound, or - for that matter - a 10mm wound.

It's an old cartridge, based on ideas from the start of the 20th century, but will still do everything you need a handgun bullet to do. You will, however, pay for the privilege; even during times of plentiful ammunition, it's about double the cost of 9mm.

10mm History and Purpose

10mm ammo

The 10mm has an interesting development history. The idea for the cartridge was basically to modernize the .38-40, a 19th century revolver cartridge that used a .40 caliber bullet and typically produced muzzle velocities of about 800 to 1000 fps with a 180-grain projectile.

The cartridge was conceived by Col. Jeff Cooper, founder of Gunsite and the guy who invented the Four Laws of Gun Safety that we've all heard. The parent case was the .30 Remington (basically a rimless .30-30) cut down to 0.992 inches in length and necked to seat a .401-caliber bullet.

Cooper's original specifications were a 200-grain bullet at 1,000 fps, yielding 450-ish ft-lbs of energy. Development was handed to Norma, whose finished product was a 200-grain bullet at 1,200 fps and 635 ft-lbs of energy, superior to most .357 Magnum loads.

The FBI adopted the 10mm after the 1986 Miami shootout, but quickly found issues. Problems with the S&W 1046 pistols showed up early, including QC issues with the guns and agents having some issues including both recoil control and the large frame of the 1046, which gave agents with smaller hands/shorter fingers fits. 

The FBI found a lighter loading could still achieve the same ballistic performance benchmarks and had the cartridge watered down to a 180-grain projectile at about 1,100 fps with less recoil. The new load, dubbed the "FBI Lite" was issued for a brief period until Smith and Wesson developed the .40 S&W cartridge which could be used in a pistol with a 9mm frame. 

And therein layeth the beauty of the 10mm Auto. You can shoot light loads, you can shoot spicy loads. It qualifies as Major in competition, it's good for defense and is a good cartridge for hunting with a handgun with the right load and responsible range for harvesting game with a pistol.

Just as with the .45 ACP, some people believe the 10mm has magical powers it just doesn't have. It is nowhere near a "guaranteed one-shot stopper" from a pistol. However, it is one of the most useful handgun cartridges in terms of all the applications a person could use one for.

Great 10mm Cartridges

10mm cartridges are some of the most popular rounds on the market and there are many great choices to choose from. Here are some of our favorites:

Federal Hydra-Shok JHP: These rounds are some of the most popular defensive rounds on the market and for good reason. They offer excellent stopping power and penetration.

Other choices are Hornady Critical Duty FlexLoc, Winchester Ranger T-Series, and Speer Gold Dot: each of these rounds also offers excellent penetration and stopping power making them a great option for 10mm ammo.

For outdoor use, Buffalo Bore Outdoorsman 220-grain Hardcast is a potent solid for large predator defense. For handgun hunting, Federal's Fusion 200-grain JHP for light-skinned game or 200-grain Swift A-Frame bonded hollowpoint loads would be fantastic starting points.

But Out Of Nowhere…45 Super!

Guy shooting a 45 handgun

Unbeknownst to some, there is a variant of .45 ACP that went to the Dark Side. It's called .45 Super, and it makes a compelling argument for itself.

As you see in the chart above, .45 ACP is loaded light relative to its case capacity; while 10mm is high-pressure and high-velocity for a pistol cartridge, .45 ACP is loaded to lower pressure and lower capacity despite clearly having more room in the case for powder.

Well, some people noticed. In fact, some people noticed quite some time ago.

Winchester cooked up a .45 caliber magnum cartridge back in the 70s, the .45 Winchester Magnum, which was intended for use in the boutique semi-auto magnums like the Wildey and AMT pistols. Detonics created a compact version, the .451 Detonics Magnum, which cut .45 Win Mag brass down to 0.94 inches, which was on purpose so no one would try to chamber it in a gun made for .45 ACP.

Dean Grennell, chief editor of Gun World magazine, trimmed .451 Detonics brass to .45 ACP length and started working up loadings along with some design input from others to figure out what needed to be done for a .45 ACP pistol to safely run the ammunition.

The classic load of .45 Super boosts a 230-gr projectile to 1,100-ish fps and 620-ish ft-lbs of energy, and a 200-gr load to the same specs as the original 10mm Norma load.

So it is possible, with a pistol converted to .45 Super, to get hot 10mm ballistics...but at 28,000 psi of chamber pressure. It hits just as hard but wears less on the pistol.

10mm vs 45 acp: is 10mm Better?

45 ACP handguns

The question of whether 10mm is "better" than .45 ACP is actually silly. Better how? Better for what, exactly? There are some modest benefits to 10mm, but how much that matters to you depends on you.

On paper, the 10mm creates more impressive numbers. The loadings are more diverse. You get 1 to 2 more cartridges in a magazine. The Colt Delta Elite holds 8+1 in a flush fit magazine compared to 7+1 in a GI magazine for .45 ACP and the Glock 20 holds 15+1 compared to 13+1 in the standard magazine of a Glock 21 in .45 ACP.

So, more bullets.

That has an advantage in competition, as both 10mm and .45 ACP comfortably make Major Power Factor.

Competition shooter

That said, .40 S&W and .38 Super also make major, which have been the smart guy guns for some time...and a lot of those guns have a 1 or 2 round capacity advantage (depending) over 10mm. Not always, but they can. Further, USPSA rule changes in 2022 and 2023 actually classify warm 147-grain 9mm loads in Major Power Factor, all but negating the need for a larger caliber except for Single Stack division...but SS division specifies a .45 caliber requirement!

10mm is the better woods cartridge. It offers more power than .45 ACP (though .45 Super equals it) and has a flatter trajectory; even .45 ACP+P loads have roughly twice the drop over the same distance as 10mm. The same applies for .45 Super; big bullets start to drop earlier.

10mm is typically more expensive than .45 ACP even in the best of times. If the typical box of 50 hardball practice rounds is $20 to $25 for .45 ACP, it can be upward of $35 for a box of 50 in 10mm depending on brand and box. But expect to pay more. 

Then we come to the question of which is better for self-defense.

It doesn't matter. Carrying a quality hollow point and placing it correctly is all that does. Pistol calibers generally stink at stopping people unless the shooter does their job as a marksman.

In Greg Ellifritz's caliber study (which uses data that includes modern ammunition, unlike earlier studies by others like Marshall and Sanow) .45 ACP has barely any edge over 9mm.

While there isn't a direct 10mm vs 45 comparison in the data, .40 S&W is - which 10mm light loads are identical to - and it is only marginally better than 9mm. .357 Magnum (both standard and .357 Sig) had a marginal edge over 9mm, but - again - only marginal, and hot loads of 10mm are roughly in the same ballpark.

In other words, both work for self-defense but neither works so well that it merits picking one over the other. 10mm is said to have better characteristics shooting through barriers, but that is rarely an issue for the armed citizen. 

Also, and this is something that True Believers don't know or don't want to admit, but 230-grain FMJ - the classic .45 hardball load at 830 fps - actually penetrates deeper in gel tests than a 10mm hollow point. In fact, .45 hardball penetrates to about the same depth in gel tests as .308 Winchester.

It turns out extra velocity doesn't really always get you what you think it does!

So which is "better"? Depends on what you mean.

Technically, 10mm does have that capacity edge for competition, but it's a moot point since 9mm makes major as do .40 and .38 Super. 10mm is a fantastic outdoors gun, with hot loads equal or better than .357 Magnum, viable for hunting or predator defense...but so is  .45 Super, and in actuality .45 ACP FMJ makes a better woods load than many realize given how well 230-grain punches through basically anything besides glass or sheet metal.  

Neither is better as a self-defense cartridge against two-legged predators. A quality bullet, placed where it needs to be, is going to work almost regardless of caliber. 

Neither cartridge nor the respective pistols are inherently more accurate than the other. Light loads of 10mm and standard-pressure loads of .45 ACP are going to have comparable recoil in terms of the recoil energy; hot 10mm will be snappier. And 10mm will be more expensive to shoot.

In reality, it's a wash unless you want a literal do-it-all gun, which 10mm does well.

Which one do you like more? Let's take our 10mm vs 45 discussion to the comments below.


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Writer sam hoober