XM511 Heavy Grenade Launcher

The XM511 Heavy Grenade Launcher is a weapon mounted onto the MAAT-9 Wolverine anti-aircraft vehicles for use as a secondary weapon to defend it against ground attacks by infantry or vehicles.

Trivia

 * A Marine in the passenger seat with a similarly named model, the XM510 Multishot Grenade Launcher, can be added to a Warthog after the Grenadier upgrade has been researched.
 * The Halo Wars: Official Strategy Guide mistakenly refers to it as both the "XM511" and the "XM510". However, later, it's correctly labeled as the XM511 and the XM510 is used to designate the hand held version carried by Marines riding in Warthogs.