The 10mm Auto (also known as the 10×25mm, official C.I.P. nomenclature: 10 mm Auto, official SAAMI nomenclature: 10mm Automatic) is a powerful and versatile semi-automatic pistol cartridge introduced in 1983. Its design was adopted and later produced by ammunition manufacturer FFV Norma AB of Åmotfors, Sweden.
The 10mm was selected for service by the Federal Bureau of Investigation (FBI) in 1989 in the aftermath of the 1986 FBI Miami shootout. During the testing and development process, the FBI Firearms Training Unit developed a downloaded version of the 10mm cartridge which they felt provided adequate performance while minimizing recoil and muzzle blast. It is commonly claimed that this reduced loading was developed as the result of complaints or training problems involving agents who were issued the 10mm, but the reduced loading was developed before any pistols were issued. The cartridge was later decommissioned (except for use by the Hostage Rescue Team and Special Weapons and Tactics Teams) primarily due to problems with the S&W 10mm issue pistols which were recalled in 1991. That same year, the FBI began issuing SIG pistols chambered in 9mm as an interim solution while problems with the S&W 10mm pistols were being worked. In the meantime, S&W and Winchester developed the .40S&W cartridge which duplicated the performance of the FBI’s reduced 10mm loading but in a shorter package which was suited for use in pistols sized for the 9mm cartridge. The .40S&W was introduced in 1990, but the FBI didn’t adopt it for some years thereafter. The FBI eventually switched to the .40 S&W cartridge, and began issuing .40S&W pistols to agents in 1997. The .40S&W remained the FBI’s issue cartridge until they reverted to the 9mm in 2015.
