Diamondback Barrels Medium Profile Barrel, 556NATO, 16 Barrel, 1:9 Twist, Carbine Length Gas System, Nitride Finish, Black 556C16M50B9 Diamondback Firearms began in 1989 with a desire to create products without compromise. Since then Diamondback has developed some of the most efficient AR15 and concealed carry pistol platforms available.