• Initially made by Norma and chambered in the Bren Ten pistol in 1983 the 10mm Auto was right off a formidable round. While the Bren Ten was not successful, the 10mm cartridge was. In 1989 the FBI announced the 10mm Auto as their officially favored sidearm. While the cartridge has proven itself over time, many felt that the cartridge was a little long for semi-auto pistols, making the pistol grip a little big for some comfort levels. When the shorter .40 S&W cartridge with very similar ballistics was introduced, it soon won popularity over the 10mm round. The 10mm Auto cartridge still has a strong following and manufacturers are still making pistols chambered for this round.