.40 S&W (Short & Wimpy) Overview The  .40 S&W  is a rimless pistol cartridge developed jointly by major American firearms manufacturers Smith & Wesson and Winchester. The .40 S&W was developed from the ground up as a law enforcement cartridge designed to duplicate performance of the Federal Bureau of Investigation's (FBI) reduced-velocity 10mm Auto cartridge which could be retrofitted into medium-frame (9mm size) semi-automatic handguns. It uses 0.40-inch (10 mm) diameter bullets ranging in weight from 105 to 200 grains (6.8 to 13.0 g). Stats Ammunition Type Damage Bullet Velocity (m/s) Barrier Penetration Armor Piercing FMJ 5.13 347.5 0.409 3 JHP 8.36 353.6 0.322 3 Subsonic 7.37 274.7 0.388 3 Note: Barrier penetration represents the rounds ability to go through walls and barriers. Armor piercing represents the rounds ability to penetrate body armor plates.