40mm Grenade Launcher

"“The only thing I can think of that would make the (MA5C) any sweeter would be an under-slung shotty or a forty mike mike.”"

- Anonomous UNSC Serviceman

The 40mm Grenade Launcher, also known colloquilly as a Forty Mike Mike by UNSC Marine personnel, is an attachment available for the MA5B and MA5C Assault Rifles. Though never used in the games, it was originally meant to be part of the MA5B during the development phase of Halo: Combat Evolved, while it was still intended for the PC. As such, its canonicity was debatable until mentioned by Bungie in a description of the MA5C.

The attachment is fitted under the barrel, replacing the flashlight attachment standard to the MA5 series. Presumably, based on its designation, it fires 40mm grenades at the user's targets. Grenade launchers of this type have been in usage since the mid and late 20th Century.