AR-15 pattern pistol caliber carbine in .40 S&W. The K40 used a blowback action in a dedicated .40 cal lower, accepting modified magazines. A law enforcement-friendly caliber choice at a time when .40 S&W was becoming the dominant duty pistol cartridge. Type: Rifle Action: Semi-Automatic Caliber: .40 S&W Capacity: 22 Year introduced: 1997, United States Weight: 80 oz Overall length: 32.5" Status: Discontinued Intended use: Law Enforcement, Recreational Shooting