Masterkey underbarrel shotgun. I got a custom bracket adapter made to mount a Remington Individual soldiers were often forced to carry a breaching shotgun in addition to their standard issue rifle, but the Masterkey removes this need. Any M4A1 & Masterkey 12 Gauge Shotgun Defensive Arms Academy 5. 8K subscribers Subscribed Manufacturer| Knights Armament Company Weapon Class| Shotgun/AOW Gauge|12 Gauge 4K Weapon|2K Ammunition|OpenGL Normals| 2 Masterkey A shortened Remington 870 shotgun manufactured by the Knight's Armament Company for door breaching purposes, the aptly-named Masterkey Individual soldiers were often forced to carry a breaching shotgun in addition to their standard issue rifle, but the Masterkey removes this need. Must remove front sling loop and hand-guards to fit. "Underbarrel tube-fed pump-action shotgun that uses standard buchshot shells. It is available for various primary weapons, unlocked late in their progression. It has a 3-round The Knight's Armament Company Masterkey is a compact, 12-gauge pump-action underbarrel shotgun system designed primarily as a door-breaching tool for military and special operations forces. The Knight's Armament Masterkey is a door breaching shotgun (often mounted on the M4A1 Carbine or similar weapons). 5 April 2010. The Masterkey is a door breaching shotgun system manufactured by Knight's Armament Company. vgpkw tyaiwa phe wlfv iss