10 mm Auto

The 10 mm Auto cartridge is a powerful and versatile chambering for semi-automatic pistols, developed by ammunition manufacturer FFV Norma AB of Åmotfors, Sweden, and introduced in 1983 in the ill-fated Bren Ten pistol. Although having been selected by the FBI for use on the field, it proved too powerful to handle by many of its employees and too large for smaller handed individuals, both of which were a common problem with female agents. These issues led to the creation and eventual adoption by the FBI of a shortened version of the 10mm, known as the .40 Smith & Wesson. Although famous for its accuracy and stopping power, scarcity and high prices have made it a niche cartridge, with a small but enthusiastic group of supporters.

History

The 10 mm Auto cartridge is the brainchild of the famous firearms expert Jeff Cooper. It was intended to be a medium velocity pistol cartridge with greater stopping power than the 9 mm Luger Parabellum and better ballistics (i.e., flatter trajectory, greater range) than the .45 ACP. When Norma designed the cartridge, at the behest of Dornaus & Dixon for their Bren Ten pistol (a strengthened variant of the CZ-75), they decided to increase the power over Cooper's original concept. The resulting cartridge, introduced in 1983, is very powerful, packing the flat trajectory and high energy of a magnum revolver cartridge into a relatively short, rimless cartridge for an automatic pistol.

Despite its enthusiastic group of supporters, it has generally failed in the popularity race simply because, for many people, the full-powered loads had a tad too much recoil and blast for defense purpose usage, and its reduced loads can be duplicated in smaller guns using the 40 S&W cartridge. However, in its lighter loadings, it is the exact duplicate of the popular 40 S&W cartridge, in its medium loadings with medium bullet weights it can equal or exceed the performance of the 357 Magnum, and with full-power loads and heavy bullets it is a fine deer hunting cartridge.

The 10 mm fires its bullet at high velocity, giving it a less-curved flight path and less drop or rise above point-of-aim compared to many other handgun cartridges, and thus is often described as "flat-shooting." Its outside diameter is also somewhat smaller than the .45 ACP and therefore offers the potential for greater capacity in a comparably-sized magazine.

The 10 mm Auto has never enjoyed large-scale popularity, but nonetheless many feel that it is an excellent cartridge. It earned a reputation for battering guns early on, but this was largely due to manufacturers trying to get away with simply rechambering a .45 ACP design for the 10 mm Auto. However, the .45 ACP works at a much lower pressure and velocity, and the frame and slide designed to handle the .45 ACP cannot handle the greatly increased forces of a 10 mm Auto without substantial strengthening. Later guns (most notably the Glock model 20 and the Smith & Wesson 1006) were built around the 10 mm and, if properly cared for, would work reliably for many years and thousands of rounds.

The other issue with early acceptance was the result of manufacturing problems with the Bren Ten; the contractor who was to manufacture the magazines had problems delivering them on time, and many early Bren Tens were shipped to dealers and customers without magazines. This, combined with the high price of the Bren Ten (MSRP in 1986 was US$500), caused the company to cease operations in 1986, after only three years of manufacture. Had not Colt made the rather surprising decision to bring out their Delta Elite pistol, a 10 mm Auto version of the venerable Government Model, in 1987, the cartridge might have sunk into undeserved obsolescence, an obscure footnote in firearms history.

Due to media exposure (primarily in the television series Miami Vice), demand for the Bren Ten increased after production ceased. In the five years after production ceased, prices on the standard model rose to in excess of US$1400, and original Bren magazines were selling for over US$150 (Blue Book of Gun Values, S. P. Fjestad, 13th edition, 1992).

The FBI adopted the 10 mm Auto round in the late 1980s along with the S&W model 1076 (a short barreled version of the 1026 with a frame-mounted decocker). As agents began having difficulty handling full-power 10 mm loads, the FBI submitted a requirement for a reduced-recoil loading. This later became known as the "10 Lite", or "10 mm FBI" load. Pistol reliability problems increased with this lighter load and Smith and Wesson saw this as an invitation to create something new: a shortened version of the 10 mm. This new round was called the .40 Smith and Wesson. The .40 S&W would function in a 9 mm Luger-sized pistol; the advantage was that smaller-handed shooters could now have a 9 mm-sized gun with near-10 mm performance. The .40 S&W has become the most popular handgun caliber among law enforcement agencies in the US, while the 10 mm Auto has all but disappeared. Glock is one of the few manufacturers that still offer handguns in 10 mm. Still, 10 mm loyalists are likely to denigrate the .40 S&W as ".40 Short and Weak" or ".40 Small and Wimpy".

Since its introduction, the 10 mm Auto has enjoyed an enviable reputation for accuracy which the shorter cartridge seems unable to match. Today, it is enjoying a bit of a resurgence in popularity, but ammunition is still expensive and can be hard to find. Most avid 10 mm shooters today are handloading due to the price of factory-loaded ammunition which may go as high as US$37 for 25 rounds. Recently, companies such as DoubleTap Ammunition have begun offering full power 10 mm Auto loads in "common" price ranges. This will surely help the 10 mm platform regain popularity.

Performance

The 10 mm Auto falls between the .357 magnum and the .41 Magnum in muzzle energy for popular loadings. For example, some standard commercial loadings are as follows: .357 Mag: 584 ft·lbf for 125 gr @ 1450 ft/s; 10 mm: 676 ft·lbf for 180 gr @ 1300 ft/s; .41 Mag: 788 ft·lbf for 210 gr @ 1300 ft/s; however, the 10 mm load given is about maximum for standard-pressure loads while the .357 and especially the .41 Magnums are commonly handloaded to significantly higher levels than these samples. Recoil energy of full-power loads is also comparable, being 9.4, 11.0, and 15.6 ft·lbf respectively for these loads (computed using the same powder and weight of gun). The 10 mm Auto is good for deer or other medium game at short range. Most 10 mm handguns are not designed for the longer range shooting often desired in hunting; a few revolvers (using half-moon clips to adapt the cartridge) are made in this chambering, and are a superior choice for hunters. Most commercially manufactured 10 mm ammunition is closer in performance to the "FBI load" than the full power 10 mm; these still offer high stopping power for defense applications, yet their recoil is more comparable to the .45 ACP in similar guns. A few smaller companies offer full-power ammunition for this chambering. Due to the limited availability and high cost of commercial ammunition, it is more a handloader's cartridge than most other popular auto pistol rounds.

The 10 mm Auto cartridge operates at very high pressure in comparison to other defensive pistol cartridges, such as the .38 Special or the .45 ACP. Its maximum average pressure of 36,000psi is closely comparable to that of the .357 Magnum or the .44 Magnum, allowing it to develop true "magnum" velocities. Original loading was a 200 grain (13 g) bullet at 1200 ft/s (366 m/s), yielding 635 ft·lbf (861 J) of kinetic energy at the muzzle. Today, Cor-Bon/Glaser lists a 180 gr "Hunter" loading of 1320 ft/s and 696 ft·lbf (943 J). This is nearly twice the energy of a .45 ACP. Double Tap Ammunition offers a 135 gr loading at 1600 ft/s producing an astonishing 767 ft·lbf (1040 J) of energy!

Muzzle velocity

* 10.9 g (170 gr) full metal jacket: 405 m/s (1330 ft/s)
* 12.9 g (200 gr) full metal jacket: 360 m/s (1180 ft/s)
* 14.3 g (220 gr) LTC, over IMR 800-X: 366 m/s (1200 ft/s)
* 11.6 g (180 gr) JHP, over IMR 800-X: 427 m/s (1405 ft/s)

Usage

The 10 mm Auto is suitable for hunting medium-sized game at moderate ranges and is certainly more than adequate for defensive or tactical use. In fact, the 10 mm Auto is one of the few true semiautomatic, rimless cartridges that is legal for hunting Whitetailed Deer in many states.

Today, the 10 mm Auto cartridge is generally used to fend off medium-sized dangerous animals, as a high-powered defensive handgun, and for hunting, especially by those who prefer the flatter carry profile and higher cartridge capacity of an automatic pistol versus a magnum revolver. It is an excellent personal defense cartridge for those who can handle its recoil and are willing to carry a fairly large pistol. It is also an inherently accurate chambering, and one that easily makes major in IPSC.

Despite the FBI switching to the .40 S&W there are still a number of law enforcement agencies that issue the 10 mm including the Albuquerque N.M.P.D. , Anniston, Alabama P.D. and Billings Montana Police Department.

The 10mm's relatively flat trajectory has been regarded by some as moot in self-defense situations against human antagonists, given FBI statistics that indicate the average self-defense shooting takes place at 7 yards (21 feet) or less.

Synonyms

*10 mm Auto
*10 mm Automatic
*10 mm Norma
*10 mm FBI

10 mm Auto: Encyclopedia BETA