10mm Auto (10×25)

The 10mm Auto (10 x 25) cartridge was created in a search for the “ultimate” combat round. While duplicating the terminal effectiveness of such proven “man-stoppers” as the .45 ACP or .357 Magnum, it is designed to provide a bigger magazine capacity when compared with the .45 and be better suited for semi-automatics when compared with the .357. This cartridge retained the overall length of .45 ACP, so it could be used in rebarrelled pistols originally designed for the .45; the case was entirely new. Originally only loaded  by Norma of Sweden from 1983, this load was first used in the US-made Bren Ten pistol and later on in Colt’s Delta Elite.

In around 1988 this cartridge was picked up by the US Federal Bureau of Investigation (FBI) as a replacement for the 9×19 Luger/Parabellum, which proved itself inadequate on several rather bloody occasions, such as the infamous Miami massacre of 1986. Smith & Wesson quickly produced several pistols in this chambering, and Heckler & Koch of Germany made a limited number of its MP5 sub-machine guns in 10mm for FBI agents. However, the FBI and several other US law enforcement agencies soon discovered that this cartridge in its original loading was poorly suited for many officers because of its severe recoil, and the FBI quickly adopted a reduced-charge loading, which then lead to the shorter .40 S&W cartridge described above. Today, this round is most popular in the USA among civilian shooters, where it is used for self-defence and hunting. Several companies still make guns in this calibre, such as Tanfoglio of Italy and Glock of Austria.

The 10mm Automatic has a straight, rimless case, usually made of brass. Most common loads include various types of expanding or jacketed bullets.