The 10mm Automatic ranks as one of the most versatile auto-loading pistol cartridges and is capable of serving for defense and taking deer-sized game, and it can be extremely accurate.  The 10mm dates back to the 1970s when several individuals (including Jeff Cooper) began cutting down .30 Remington cases and loading them with .40-caliber bullets from the 38-40 Winchester and .401 Herters Power Magnum cartridges, then firing them in a modified Browning Hi-Power pistol.  The concept had great potential but probably would have sat dormant had it not been for Tom Dornaus and Mike Dixon.  They finalized the cartridge dimensions and introduced the Bren Ten auto-loading pistol in 1983.  Norma began producing ammunition, and the 10mm Auto was born.  Early ballistics were impressive, pushing a 200-grain bullet to around 1,200 fps.

Following the Bren Ten production problems, Smith & Wesson and Colt began making pistols, and the FBI adopted the cartridge.  The recoil of the 10mm led to many law-enforcement requests for lighter loads, which typically pushed a 180-grain bullet between 980 to 1,030 fps.  With this reduction in power, Smith & Wesson shortened the case, installed a small pistol primer and named it the .40 S&W (1990).  In so doing, the company was to duplicate “10mm Lite” ballistics and fit the new cartridge into smaller and lighter guns.  This resulted in extreme popularity for the .40 S&W.