The Masterkey is simply a Colt M4 with a modified Remington Model 870P shotgun underneath. It's mounted and operated in the same fashion as the M203 grenade launcher. It fires 12 gauge 70mm shells, and has a capacity for seven shells. Its effective range is limited to about 10 meters when fired as a shotgun. Rather than being an offensive weapon, this is usually used to breach doors rapidly, earning its name as the master key to any door. Usually used by Special Forces.