M655 machine gun

The M655 Heavy Machine Gun/Anti-Matériel is a 20mm heavy machine gun used by the UNSC.

Design details
The M655 machine gun is a rotary autocannon employed by UNSC forces. The weapon boasts four barrels fed by two 20mm ammunition belts. When firing, the weapon takes a few second to "spool up", with the fire rate increasing rapidly over the course of a few seconds.

Usage
Some variants of the Mark IX Mantis powered exoskeleton are armed with an M655 as well as an M5920 missile launcher. Specially-upgraded Mantis variants employed by the Office of Naval Intelligence security forces employ an M655 upgraded with improved heat sink shrouds, allowing the weapon to fire for longer before overheating. Mantises modified by Isabel for use by forces in the Second Ark Conflict saw the M655's lower housing removed and replaced with a large drum magazine.

Trivia
In Halo 4, the M655's barrels do not spin when the weapon is fired.

List of appearances

 * Halo 4
 * Spartan Ops
 * Halo: Escalation
 * Halo 5: Guardians
 * Halo Wars 2