The Remington Masterkey is an American underbarrel shotgun, essentially a cut-down Remington Model 870. Its intended purpose is to breach locked doors with excessive violence, allowing assault teams to get in and sweep. However, it can also shoot someone in a pinch. The Masterkey is primarily marketed towards American special forces and law enforcement, but it is shipped internationally and there are a number of them in Oceanyka (though in short supply).
Underbarrel Device
This weapon isn't really designed to be fired standalone, but rather fit under the barrel of a rifle.
Unto the Breach
The Remington Masterkey is a tool for urban combat, designed to allow a breaching team to sweep buildings more efficiently.