The KAC M203 40mm grenade launcher can be mounted onto SR-16 rifles, with the KAC QD mount. They can also be deployed solo with the KAC Standalone modules. Two M203 barrel lengths are available: (9" and 12").

The 12-gauge Masterkey shotgun can be mounted under standard rifles as a breaching tool when used with special ammo. It is also mountable to KAC's Standalone Module. The system consists of a Remington 870 shotgun that can be mounted onto a M4 rifle in an under-barrel configuration. The shotgun has a 3 round capacity and should be only operated when attached to a host rifle or the Standalone Module.

The M203 and Masterkey is designed exclusively for Military and Law Enforcement applications.