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A History of the 10mm Auto

A History of the 10mm Auto


Most of our readers know that Colonel Jeff Cooper loved the 1911 and thought that it was and is the best option for those serious about pistolcraft. There are books about both the man and his love for the 1911. However, while Col. Cooper was a devout worshipper of the .45 ACP, he also expressed an interest in a pistol caliber capable of pushing a 200-grain bullet at 1,200 feet per second. And he thought that such a caliber would be ideal for times where we might require a pistol to reach out to 50 yards.

Pursuant to this goal, Col. Cooper played a prominent role in developing and designing the Dornaus and Dixon Bren Ten. He expressed optimism for both the pistol and the caliber, as he felt they brought a new level of ballistic performance to the pistol shooter. The Bren Ten was a CZ 75-based pistol designed around a new and powerful cartridge, the 10mm Auto. The Bren Ten and the 10mm Auto cartridge enjoyed a surge in popularity in the early- to-mid-1980s, but manufacturing and supply problems doomed the pistol and the cartridge, with both on life support.

Then, on the morning of April 11, 1986, eight Miami FBI agents spotted and approached two wanted bank robbers. In the ensuing firefight, Special Agents Dove and Grogan were killed as well as the two bank robbers, Matix and Platt. The event shocked the nation as well as the law enforcement community. The autopsies of the two crooks revealed that the then-issued FBI service round, a 9mm, lacked sufficient penetration to readily incapacitate. Had one round penetrated Platt's body an inch more, it's likely that the two FBI agents would have survived the encounter. This real-world event became a driving force behind the 10mm Auto and validated Cooper's idea that magnum-level ballistics in a semiauto had serious application in the law enforcement world.


With the FBI declaring their service handguns deficient in "stopping power," the search began in earnest for a more powerful cartridge capable of penetrating to incapacitating depths. The FBI selected the 10mm Auto cartridge as its new service round and issued new pistols to all of its agents.

Neutering the 10mm Auto

Even though the FBI shootout in Miami occurred in my youth, as did the adoption of the 10mm Auto by the FBI, I still remember following these developments in earnest. To a young mind, "more power" are the magic words whether we're talking horsepower or ballistics. The idea of having a semiauto pistol capable of magnum performance seemed like a great idea to me (it still does).

After a series of tests using the 10mm Auto in both pistols and submachine guns, the FBI adopted the cartridge. I don't know who the agents were who supervised the tests and adoption, but I think those men deserve medals. To a proficient law enforcement officer whose primary and often only weapon is a pistol, the 10mm Auto is the best choice.


The FBI, like any other organization or company, has a few truly brilliant minds desperately trying to shepherd the remaining masses of the mediocre. While the choice to adopt the 10mm Auto was brilliant, the majority of FBI agents are accountants and lawyers by trade. There is no rule mandating firearms incompetence from lawyers and accountants, but in the FBI's case that is exactly what happened. The 10mm Auto was just too much of a good thing for most of the agents to shoot well, so the FBI neutered the 10mm by loading it down to more manageable velocities. This load became know as the "10mm FBI." Notice that no ammunition manufacturer wanted to put their name on this most heinous travesty. I applaud the industry's taste and sound judgment.

In no time at all shooters realized that the 10mm had a lot of unused case capacity when loaded for sissies and decided to shorten it. This abbreviated 10mm Auto became the .40 S&W, which has since become the most prevalent cartridge issued to American law enforcement. If I had to give an award to the .40 S&W it would be "Most Irrelevant." It doesn't shoot big bullets like the .45 ACP, pistols chambered in it can't hold as many as the 9mm, and it can't come close to the ballistics of the 10mm Auto. It is a cartridge of compromises that makes perfect sense to law enforcement administrators who usually know nothing about firearms and competition shooters looking to make the "major" power factor. For serious business, go with the 9mm, .45 ACP or 10mm.

Guns in 10mm Auto

The pistol that got the whole 10mm Auto movement on its feet was the Bren Ten, later immortalized in the T.V. show "Miami Vice." Production issues eventually spelled the demise of the Bren Ten, but Smith & Wesson picked up the torch with their Model 1076 — the pistol that the FBI adopted — and the Model 1006. Colt also produced the Delta Elite, the first 1911 pistol to be chambered for 10mm Auto.


Pistols currently offered in 10mm can be found from the custom 1911 makers of Nighthawk and Wilson Combat. Colt has also returned to offering limited quantities of the Delta Elite each year. The 1911 you see here is Nighthawk's longslide that features a six-inch barrel. The 1911 is an excellent choice for the 10mm because of its familiar controls and comfortable ergonomics. When combined with the integral feed ramp, a 1911 in 10mm becomes as durable as it is comfortable.

On a normal 1911, there are two ears that protrude from the bottom of the barrel and straddle the link. On this Nighthawk pistol and shown in the photo, the integral feed ramp provides a solid foundation for the barrel link and enables Nighthawk to simply recess the ramp into the frame to accommodate the link. Where there are normally two long ears, there is now a solid chunk of steel.

The ears supporting the barrel link of a custom 1911 are often the first things to fail due to improper fit. It seems that if they're going to break, it'll happen in the first 5,000 rounds. With the Nighthawk pistol, there is a solid piece of steel in place of the ears so we no longer have to worry about them shearing off. The 1911s made in this fashion are ideal for the 10mm and ensure that the pistol is capable of handling even the stoutest loads.

Para USA announced at the 2012 SHOT Show that they would be making a long-slide 10mm with a six-inch barrel and a double-stack magazine. It hasn't made it to production yet, so we'll just have to keep our fingers crossed for now.


Glock makes the Models 20 and 29 in 10mm and has for a couple of decades. These pistols offer full-size and compact options for those who favor striker-fired polymer pistols. EAA also makes a couple of Witness models in 10mm. The EAA pistol is a large CZ 75 variant for those who favor the ergonomics of that style over the 1911s and Glocks.

Uses for the 10mm Auto

The 10mm Auto closely matches the ballistic performance of the .41 Magnum in bullet weights and velocities. The 10mm is ideally suited and has a substantial edge over any other semiauto caliber in two key domains: hunting and select law enforcement scenarios.

Hunting with a 10mm is a no-brainer thanks to its heavy bullets and high velocities. Many of the longslide 1911s are built expressly for that purpose. Whether it's hogs or whitetails, the 10mm Auto is the way to go in a semiauto pistol. Hornady has loads with 180- and 200-grain bullets that are exceptional choices for both activities.

I, like Colonel Cooper and straight-thinking FBI agents, also believe that the 10mm round is an excellent choice for law enforcement. We often make most decisions in the aftermath of a crisis. When the FBI wanted their lack-of-penetration problem fixed, they chose the 10mm. Especially when we consider that law enforcement shooting scenarios often involve shooting through barriers, the higher velocity of the 10mm Auto is a real advantage. A quick perusal of officer-involved shooting videos on the Internet shows that many of these fights occur in and around vehicles. The 10mm is our best option in these situations where we might have to shoot through steel and glass and still have lethal penetration on the target.


The sidearm is also the primary and only weapon for many law enforcement officers. As such, it's important for cops to carry as much gun as they can comfortably handle. I was never a police officer, but I carried a sidearm in Iraq and Afghanistan and can think of a couple of times when I wished I had something bigger, usually when there was a barrier I needed to punch through or the distances to the target increased.

An eternal principle of gunfights reads thus: Bring enough gun. When we're relegated to only carrying a pistol, we should make it a point to carry as much pistol as possible for those times when the unexpected happens. No other semiauto pistol caliber offers the range or penetration of the 10mm. For law enforcement officers who face the violent and unexpected, the additional performance of the 10mm Auto is comforting.

At the Range

One of the major gripes critics of the 10mm have is the recoil it generates. This was the primary reason the FBI cited when they decided to move away from traditional loading of the 10mm Auto. There was just too much recoil for their agents.

Gauging a round's potential and success by how marginally trained shooters perform with it is folly, and it's a shame the reputation the 10mm acquired at their hands. The 10mm recoils no more than a Government-model .45 ACP or a Glock 19 in 9mm. The .45 shoots a much heavier bullet, and the Glock 19 is a lighter gun. Bullet and pistol weight both play a key role in perceived recoil. The longslide 1911 seen here loaded with 180-grain bullets moving at 1,250 fps generates identical amounts of felt recoil as the .45 and the Glock.


The ammunition I used to generate the data for this article comes from Hornady's Custom line and had bullets weighing 155, 180 and 200 grains. The XTP bullet is an exceptional choice for the 10mm Auto, as it features a thick jacket that handles the high velocities well and ensures the bullet stays together for deep penetration.

I fired the three Hornady loads through the Nighthawk longslide with a six-inch barrel and a Glock Model 20 with its 4.6-inch barrel. The difference in barrel length generated an approximate 80 fps difference with each load. I collected the muzzle velocity data on an Oehler 35P.

Colonel Cooper and the FBI correctly identified the need for a flat-shooting semiauto pistol cartridge for law enforcement use. A heavy bullet (180 to 200 grains) moving at high velocity (1,200 fps) offers excellent performance for those select times when ranges extend or we need to shoot through a barrier. The 10mm Auto is the cartridge for this application. Hornady's XTP bullets and their thick jackets are an ideal pairing for the 10mm with their 155-, 180- and 200-grain loadings that allow the 10mm shooter to confidently do everything he needs from self-defense to law enforcement duties.

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