10mm Research

In my continuing research of 10mm defense loads: Let me start this post by pointing out that pistols are a compromise, in that they all suck for self defense. We carry them because it is easier and gets you fewer sideways looks than does carrying a long gun. Better the handgun on your hip than the firearm at home in the safe.

The current 10mm that I have is a full sized M&P10mm and I am unlikely to carry it. I find that I don’t even carry any of my full sized handguns on a regular basis. What I find myself carrying most often is a J frame .38 or a Shield Plus in 9mm. Still, buying and shooting guns is fun, so what the hell?

Even though I won’t carry it much, I always keep plenty of magazines and ammo on hand for every firearm. Five magazines for every pistol is the minimum I am comfortable with. For ammo, the minimum is 500 rounds for semi auto handguns, 100 rounds for revolvers, and 1000 rounds for semi-auto rifles of “war shots” that I like to keep on hand. That doesn’t count whatever range ammo that I have.

Of course I am going to research this, because it’s what I do. See the months of research I did before going with solar as a backup power system.

In looking at defensive ammo, the most important criteria is that it functions well in my firearm. It needs to go bang every time I intend it to. I will accept no more than one failure for every 500 rounds. (That’s why I no longer carry and have sold most of my 1911’s. They jam far too often. See this post here about the suckage that was my experiment with that platform.) Going along with that, the ammo must also be somewhat accurate for my handgun. That means passing a 5×5 test- I have to be able to put 5 rounds into a 5 inch circle at 5 yards in 5 seconds or less while drawing from a holster. I would rather hit with a .22 than miss with a .44.

The next criteria is that it has solid performance. There is no point in reinventing the wheel- I use the FBI criteria that states a bullet should penetrate between 12 and 18 inches of ballistic gelatin and a bullet that expands to at least 1.5 times its diameter. With handguns being poor performers, I want to maximize what performance I *do* get, so I try to only buy and stock ammo that meets this standard. I expected that my research will find more full power 10mm that goes beyond the 18 inches than falls short.

In 1983, Whit Collins, John Adams, Irving Stone, and Jeff Cooper worked with Norma AB to design the 10mm Automatic cartridge. Their goal was to create the a handgun cartridge that fired a heavier and larger caliber bullet than the 9mm Luger at a higher velocity and magazine capacity than the .45 ACP. This would create a handgun cartridge that combined the best of both platforms.

They did this by cutting a .30 Remington case down and loading it with .40 caliber bullets from the .38-40 Winchester. they not only achieved that objective but exceeded it by a healthy margin. The original 10mm Auto load shot a 200 grain projectile at 1,200 feet per second for 640 ft-lbs of muzzle energy, which was a significant step up in performance compared to the 9mm Luger and the .45 ACP. The new round nearly doubled the energy of the 9mm Parabellum and off the shelf .45 ACP ammunition.

Dornaus & Dixon Enterprises worked in parallel with Jeff Cooper and the rest of the 10mm Auto team to build a handgun designed specifically to shoot the new cartridge: the Bren Ten pistol. Similar in appearance to the CZ-75, Sonny Crockett in the television show Miami Vice helped make the Bren Ten famous. For this reason, demand for the pistol and the cartridge exploded in the mid-1980s. Unfortunately, the Bren Ten was rushed into production and the pistol’s reputation suffered due to early issues with reliability, quality control, and a shortage of magazines. The company was never quite able to regain its footing after those initial missteps and declared bankruptcy in 1986 after only making 1500 of the pistols. Shortly after the passing of the Bren Ten, Colt rolled out a Model 1911 modified to use the cartridge that they named the Delta Elite. 

Then came a fateful day in US law enforcement. The 10mm Auto piqued the interest of the FBI during their search for a more powerful service round in the aftermath of the disastrous 1986 shootout with two bank robbers in Miami.

The FBI liked the 10mm and originally wanted to switch to that platform, but the fact that they had a lot of limp wristed agents who were recoil sensitive, they wanted something with less recoil. The FBI test report on the cartridge was apparently labeled:

CAUTION: Velocities, pressures and recoil are extreme, vary greatly, and damage weapons with extended use. Control for multiple shots extremely difficult.

They downloaded the 10mm to reduce power by about 30% and issued a request for handgun makers to bid on a new cartridge/handgun combination for FBI use. This loading became known as the “10mm FBI load.” This load was several hundred feet per second slower than the original 10mm Auto, but the FBI was still satisfied with its penetration and terminal performance.  The winner of this competition would get a lucrative contract to supply most of US law enforcement.

Enter Smith and Wesson. They developed a cartridge that was shorter than the 10mm and met the FBI standard, and the .40 S&W was born. Derisively, it is said that S&W in this case stands for “Short and Weak.” Many of the advantages of the powerful 10mm cartridge disappeared with this downloaded cartridge. Instead of getting all of the combined advantages of the 9mm and .45ACP, you got none of them. That’s why the .40S&W has largely fallen out of favor- there is no advantage of having it.

To be completely honest, I own several .40S&W pistols, but I can’t remember the last time I carried or even shot one of them. Less capacity and slower bullets than a 9mm, lighter bullets than a .45ACP. What’s nice is that I can swap a barrel and change my S&W40 to .357Sig or 9mm.

I don’t want to simply buy 10mm ammo that is loaded to 40 caliber specs. If I wanted to do that, I would just carry one of my 40 calibers. I was looking for an ammo manufacturer that was loading ammo that really took advantage of the 10mm cartridge. After some searching, I like Underwood ammo as well as Fenix ammunition. Both of them are loading to the full 10mm capabilities. Buffalo Bore does as well, but their bullets are overpenetrating and seem better for large animals than for self defense.

Fenix makes one self defense loading for 10mm, and that is a 180 grain JHP moving along at 1250 feet per second, giving us a muzzle energy of 624 foot pounds. They are currently out of stock, so let’s look at our next contestant.

Underwood has quite a few loadings for 10mm. I selected the Tools & Targets YouTube channel because the guy clearly loves his 10mm and does a decent job in testing the bullets he looks at. The loadings that I am most interested in:

200 grain XTP moving along at 1250 feet per second with 694 ft/lb of energy. This round got 1100 fps out of that 4.6 inch barrel, delivering 537 ft/lb. The bullet penetrated 24 inches. That velocity isn’t great, but it’s the overpenetration that concerns me. Any energy that the bullet has when it leaves the backside of your target is wasted energy.

180 grain XTP at 1300 feet per second and 676 ft/lb. This channel saw the ammo come in right at 1242 fps for 616 ft/lb from a 4.6 inch barrel. He got a full 16 inches of penetration with the bullets retaining 150-179 grains of their mass, even though they expanded to more than .640 inches in diameter. Impressive performance.

155 grain XTP at 1500 feet per second and 775 ft/lb. The guy in this video found that it hit 1500 fps from a 4.6 inch barrel, just like the box claimed. That means it was right about 800 foot pounds of energy. The bullet gave 12.5″ to 13″ of penetration, with or without the clothing barrier.

135 grain JHP at 1600 feet per second and 768 ft/lb. The guy here got an average of about 1450 feet per second out of a 4.6 inch barrel. The wound cavity looks great, but it is only penetrating to 12.25″ and I just don’t see me wanting to use this one. I think the combination of slower than advertised speed along with the Nosler hollow point means suboptimal performance.

Overall, it looks like I will be selecting the Underwood 180 grain XTP for our initial reliability testing. I will order some, and once the reflex sight comes in, we will take a couple of hundred rounds to the range and see how it works. At $1.25 a round, it is actually cheaper than Gold Dots ($1.75) or Hornady Critical Duty ammo ($1.50). I just ordered 500 rounds for testing. If that round doesn’t work out, I will try the 155gr loading.

The disclaimer: I don’t advertise, and receive nothing for my reviews or articles. I have no relationship with any products, companies, or vendors that I review here, other than being a customer. If I ever *DO* have a financial interest, I will disclose it. Otherwise, I pay what you would pay. No discounts or other incentives here. I only post these things because I think that my readers would be interested.