Not a grenade launcher, it's a Masterkey system - underbarrel version of the Remington 870 MCS for use with the M4/M16 series. It's meant for door breaching.
Kaorin said: Not a grenade launcher, it's a Masterkey system - underbarrel version of the Remington 870 MCS for use with the M4/M16 series. It's meant for door breaching.
...and was never actually used outside of a videogame, as far as I remember.