The 10mm Automatic

By Chuck Hawks

10mm Auto
Illustration courtesy of Hornady Mfg. Co.

Norma brought the 10mm Automatic cartridge to life in 1983, for the Bren 10 pistol. The demand for this cartridge and a gun to shoot it was created by the efforts of various vocal gun writers and proponents of big bore pistol cartridges, in much the same fashion as they had whipped up demand for the earlier .41 Magnum revolver cartridge.

The much-ballyhooed Bren 10 proved to be a mechanical and commercial failure and the future of the 10mm Auto cartridge was in doubt. Colt saved the day for the 10mm Auto by chambering their Delta Elite version of the 1911 Government Model auto pistol for the faltering cartridge in 1987. Glock, SIG, S&W and others eventually introduced large frame autos for the 10mm.

The 10mm Auto approximates the .357 Magnum revolver cartridge in power. With maximum loads, the 10mm is capable of driving a 175 grain bullet at muzzle velocity (MV) of 1290 fps and muzzle energy (ME) of 647 ft. lbs. from a 5.5" barrel. This load is available from Winchester with a Silvertip JHP bullet. Needless to say, it is plenty powerful, with 649 ft. lbs. of muzzle energy (MV). As you might suspect, this load kicks like a full power .357 Magnum, too.

The 10mm Auto got a shot in the arm when it was adopted by the FBI. Unfortunately, recoil proved to be a problem with the full power 10mm for police use. The cartridge simply kicks too hard for many police officers to handle well and shooters with small hands had trouble gripping the large framed pistols required for the cartridge. Large, heavy pistols are also difficult to conceal and tiring to carry all day.

The FBI successfully addressed the recoil question by developing a lower velocity load for the 10mm Auto. This lowered the velocity to 1030 fps using a 180 grain JHP bullet (Federal figures). This has come to be known as the "10mm Lite" load and it led to the development of the .40 S&W cartridge, which eventually replaced the 10mm Auto in FBI use. However, that is a story for another article. (See The .40 Smith & Wesson.)

The size and weight problems created by large frame pistols are not so easily solved and few police agencies followed the FBI's lead in adopting the 10mm Auto. Instead, the .40 S&W cartridge has become the favorite big bore cartridge for police use. It has proven adequate for police purposes and is available in medium frame pistols.

There are a reasonable number of 10mm Auto factory loads offered by the various ammo companies. Remington loads a 180 grain FMJ bullet at 1150 fps MV with 529 ft. lbs. ME. CCI/Speer has their Blazer aluminum cased load using a 200 grain TMJ bullet at 1050 fps and 490 ft. lbs. Winchester offers the Super-X 175 grain Silvertip load mentioned above.

Federal currently offers two loads for the 10mm. The first is a Premium Personal Defense load with a 180 grain Hydra-Shok bullet at a MV of 1030 fps and ME of 425 ft. lbs. The other is an American Eagle offering with a 180 grain FMJ bullet, also at a MV of 1010 fps. Hornady also offers two loads in their Custom line, a 155 grain XTP hollow point bullet at 1265 fps / 551 ft. lbs. and a 180 grain XTP at 1180 fps / 556 ft. lbs. PMC catalogs three factory loads, a 170 grain JHP (1200 fps / 543 ft. lbs.), 180 grain SFHP (950 fps / 361 ft. lbs.) and 200 grain TC-FMJ (1050 fps / 490 ft. lbs.).

Cor-Bon offers the greatest variety of 10mm Auto factory loads. These include a Glaser Safety Slug load using a 115 grain pre-fragmented bullet at a blistering MV of 1650 fps and ME of 695 ft. lbs. Standard Cor-Bon Self-Defense JHP loads include a 135 grain JHP at 1400 fps / 588 ft. lbs, 150 JHP at 1325 fps / 585 ft. lbs and a 165 grain JHP at 1250 fps / 573 ft. lbs. Then, there is a DPX self-defense load using a Barnes 155 grain solid copper HP bullet at a MV of 1200 fps with ME of 496 ft. lbs.

In addition, Cor-Bon offers two 10mm loads specifically intended for handgun hunting. The first is loaded with a 180 grain Bonded Core SP bullet at 1300 fps and 676 ft. lbs. The second uses a 200 grain RN Penetrator bullet at 1125 fps and 526 ft. lbs. at the muzzle.

The best one shot stop percentage in the caliber, according to the study by Marshall and Sanow, belongs to the full power Winchester 175 grain Silvertip load, an excellent 92%. The 10mm Lite load has compiled a very good 82-87% record, depending on manufacturer.

The 10mm may be the most versatile of all auto pistol cartridges. Not only can the same gun shoot full power and light 10mm loads, most will also function correctly with .40 S&W ammunition. The shorter S&W case cannot headspace on its case mouth in a 10mm chamber, but the gun's extractor will generally hold the .40 cartridge against the breech face for reliable ignition. I would not have believed it if I hadn't seen it, but our Glock and SIG 10mm Auto pistols featured in Guns and Shooting Online reviews (see the Product Reviews page) worked fine when fed .40 S&W ammo. This makes the 10mm auto analogous to a .357 Magnum revolver, which can shoot all .357 Mag. and .38 Special ammo.

Reloading for the 10mm Auto is straight forward and the 10mm uses the same .400" diameter bullets as the .40 S&W. The popularity of the latter cartridge insures a decent selection of bullets.

The fifth edition of the Nosler Reloading Guide shows that 9.5 grains of HS6 powder behind their 150 grain JHP bullet gives a MV of 1156 fps, and 10.5 grains of HS6 gives the same bullet a MV of 1290 fps. These loads used Winchester cases, WLP primers and were tested in a 6" pistol barrel. Reloaders are ideally positioned to take full advantage of the 10mm Auto's versatility.

The 10mm cartridge has been promoted more as a hunting cartridge than a self-defense cartridge in recent years. The Winchester Super-X 175 grain Silvertip and 180 grain Cor-Bon Hunter bonded SP factory loads are probably the best choice for most hunting with a 10mm pistol. For protection in the field, the Cor-Bon 180 grain Bonded and 200 grain Penetrator loads are probably about as good as it gets.

The 10mm is the best hunting cartridge normally chambered in autoloading pistols and, based on our test results, the full size Glock 20, Glock 20 SF and SIG P220 pistols are sufficiently accurate to take advantage of the full power cartridge's flat trajectory. For example, the Winchester Silvertip load has a mid-range rise of only 3.3" over 100 yards.

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Copyright 2001, 2016 by Chuck Hawks. All rights reserved.