10mm Auto

[12] Although it was selected for service by the Federal Bureau of Investigation (FBI) in 1989 in the aftermath of the 1986 FBI Miami shootout, the cartridge was later decommissioned (except by the Hostage Rescue Team and Special Weapons and Tactics Teams) after their Firearms Training Unit eventually concluded that its recoil was too excessive for training average agents and police officers,[12] and that the pistols chambered for the cartridge were too large to grip well for some small-handed individuals.

When FFV Norma AB (now Norma Precision AB) designed the cartridge at the behest of Dornaus & Dixon Enterprises, Inc. for their Bren Ten pistol (a newly developed handgun with a design inspired by the CZ 75), the company decided to increase the power over Jeff Cooper's original concept.

[12] Quality control issues plagued early acceptance of the caliber, as a result of rushed production to meet numerous (some even defaulted) pre-orders of the pistol it was originally—as well as then being only—chambered for: the Bren Ten.

[14] The relatively high price of the Bren Ten compared to other pistols of the time (manufacturer's suggested retail price was $500 in 1986, the equivalent of $1,200 United States dollars in 2021[15]) was another factor in its demise, and the company was eventually forced to declare bankruptcy, ceasing operations in 1986 after only three years of inconsistent, substandard production.

Had it not been for Colt making the unexpected decision in 1987 to bring out their Delta Elite pistol (a 10mm Auto version of the M1911) and later, the FBI's adoption of the caliber in 1989, the cartridge might have sunk into obsolescence, becoming an obscure footnote in firearms history.

[16] Due to media exposure in the television series Miami Vice, where one of the lead protagonists had used the pistol as his primary signature weapon, demand for the Bren Ten increased after manufacturing ceased.

[22] The test seemed inconsistent or contradictory to future observers, and it was accused of heavy .45 ACP and American handgun bias.

[21] As the FBI was adopting a 10mm cartridge closer in bullet weight and velocity to the .45 ACP, there was a need for large amounts of newly built ammunition of this type.

With some pistol reliability problems increasing in this lighter load,[18] Smith & Wesson observed that a version of the 10mm case reduced to 22 millimeters in length from the original 25 mm could be made with the retained performance parameters of the "10mm Lite".

The shorter case allowed use in pistols designed with similar dimensions to those chambered in 9×19mm Parabellum, with the advantage that smaller-handed shooters could now have smaller-frame semi-automatic handguns.

Colloquially called the "Forty Cal" and other synonyms, this innovation since became a common handgun cartridge among law enforcement agencies and civilians in the United States, while the parent 10mm Auto remains fairly popular and has shown a resurgence in recent years particularly among hunters.

In CIP-regulated countries, every pistol/cartridge combination is required to be proofed at 130% of this maximum CIP pressure to certify for sale to consumers.

[37][38] The round makes the "Major" power factor ranking in the International Practical Shooting Confederation, even in lighter loadings.

The Bren Ten (left) and Smith & Wesson Model 610 Classic (right), 1983.