10mm Self Defense: A Suitable Defensive Cartridge?

For years—decades—9x19mm Parabellum has reigned as the go-to self-defense cartridge. Nothing can last forever, though, so maybe it’s time a new cartridge became the frontrunner. It isn’t as though none have tried. 380 ACP seems to make random surges in popularity but remains relegated to the realm of micros and backup guns; new rounds like 30 Super Carry are too unproven to own the market.

What cartridge is already proven as a stellar performer with a lot of guns chambered in it? 10mm Auto, of course. So why can’t the new hotness (which admittedly isn’t very new) be 10mm self-defense?

Who Invented 10mm?

There’s some back and forth regarding who really, truly invented 10mm. However, it’s well known the idea first came from the late Colonel Jeff Cooper.

Back in 1976, Cooper founded what’s now called Gunsite Academy—it was known as American Pistol Institute when it was new—and is respected in many circles for creating the Modern Technique of the Pistol. Cooper hung out with such pistol greats as Jack Weaver, Elden Carl, Thell Reed, and Ray Chapman. He’d spent years shooting, training, and analyzing, and decided the gun world would benefit from a bigger bore defensive round. Something that could push a 200-grain bullet at high velocities; a cartridge to outpace the 45 ACP while maintaining its bulk. Oh, and he didn’t want the new cartridge to have a significant or rapid drop on longer shots.

In 1982, Cooper and a few other dedicated shooters, like former Guns and Ammo editor Whit Collins and pistolsmith Irving Stone, decided to get going with a collaboration to create the new cartridge. It started out like a lot of cartridges do: By modifying an existing cartridge. It was the 30 Remington they decided to cut down and load with a 40-caliber bullet. With the general idea in hand, Cooper went looking for a manufacturer to fine-tune it.

According to the 1984 Dornaus & Dixon catalog, the creation of 10mm Auto went something like this:

Dornaus & Dixon Enterprises was formed in December 1979 with the combined efforts of two men, Thomas F. Dornaus and Michael W. Dixon, who had decided to build what they hoped would be the heir to the Colt .45 Auto. In January 1980, they went seeking advice from the most knowledgeable sources available. This effort naturally led to Jeff Cooper. Upon seeking his advice, it was discovered that Jeff Cooper, likewise, was working on such an arm. It was decided that Dornaus & Dixon and Jeff Cooper would join forces, with Jeff Cooper providing conceptual design criteria, as well as technical advice based on his vast practical experience, and Dornaus & Dixon providing the engineering, development, manufacturing, and marketing expertise. To retain his professional objectiveness, Jeff Cooper is not an employee of Dornaus & Dixon Enterprises, nor does he have any authority in the manufacturing of the Bren Ten.

On July 15, 1981, Dornaus & Dixon Enterprises, Inc. became a legal entity and was incorporated by the Secretary of State, in the State of California. On November 1, 1982, the manufacturing facility was dedicated in Huntington Beach, California.

Basically, Cooper went to Dornaus & Dixon Enterprises for help, and then Norma was brought in. At the time, Norma was known as FFV Norma AB (today they’re Norma Precision AB). Norma’s involvement in creating the 10mm Auto happened because Dornaus & Dixon Enterprises approached them for help. If you’re looking for a precise sequence of 10mm events, good luck. Everyone wants to claim so-and-so did this or that, leaving the 10mm’s history a little messy.

10mm Self Defense

The 10mm cartridge is a more than respectable self-defense round if the shooter is able to manage it. 

It doesn’t matter if you love or hate the legacy of Cooper and Gunsite, what matters is how well this cartridge performs. 10mm is a cartridge capable of fantastic performance, even when it isn’t loaded as hot, as most manufacturers tend to tone it down with today’s factory loads. It outpaces both 9mm and 45 ACP even when those two are loaded as overpressure rounds. Take, for example, Hornady’s Critical Duty line:

There’s no debate regarding how fast 10mm leaves the barrel of a gun compared to other handgun cartridges, but can it maintain its velocity and energy? Check out the rest of the Hornady Critical Duty comparison below:

Keeping in mind that 10mm is the only cartridge here not loaded as an overpressure, or +P, round, we can see it continues to perform well. It would appear it’s worth some consideration.

Is 10mm Good for Self Defense?

It is, but as with any cartridge, there are considerations to be aware of. The top issue mentioned when 10mm is being discussed for self-defense use is the risk of over-penetration. Because it’s a more ballistically powerful cartridge than the other common defensive loads, it does penetrate more deeply. This is what makes it such a stellar option for handgun hunting, but it could also mean it over-penetrates a two-legged predator and strikes an innocent person. Does that mean it’s a lousy idea for self-defense? Absolutely not.

10mm is a workable defensive round. It’s more than capable of stopping a threat, there are a lot of models of guns chambered in it, and it can be quite precise. Regardless of what caliber handgun you carry for self-defense purposes, you are responsible for every shot fired. That means being capable of following the four safety rules, even when you’re fighting for your life. The rules being, of course:

The 10mm was literally designed to be a superior defensive round. There are many gun owners who do carry their 10mms for self-defense use, but it isn’t exactly a mainstream practice. Whether or not it should be depends on far too many factors such as hand size and skill level. That’s because when it comes right down to it, you need to select the correct gun and caliber for your needs and abilities, not whatever is cool or popular. If that’s a 10mm, more power to you (literally). If it’s a 9mm, yes, that’s also a good defensive round.

It would be nice to see 10mm make a comeback—or would that be a first-time running as a favorite?—but it seems to be in the distant future. There are more 10mm loads being produced as well as a larger number of guns chambered in it being made. The time of the 10mm is coming. You’ll see.