M655 machine gun

The M655 Heavy Machine Gun/Anti-Matériel is a 20mm heavy machine gun used by the UNSC. Some versions of the Mark IX "Mantis" powered exoskeleton are armed with an M655 as well as an M5920 surface-to-ground missile launcher.^[1]^[2]

Trivia

Under modern military conventions, the M655's 20mm caliber would actually classify it as an autocannon.
In gameplay, the M655's barrels do not spin when the weapon is fired.

v • d • e

Heavy armaments of humanity

Artillery

Autocannons and mounted machine guns

Machine guns	M202 XP • M12 machine gun • Vulcan (M41 (ELAAGat) • M46 • M49) • M268 heavy machine gun • M655 machine gun

Autocannons	ALI-50 110mm • GAU-10/A • GAU-23/AW • M193LP autocannon • M340 autocannon • M370 autocannon • M410 flank gun • M50 Guardhouse • M638 autocannon • Machine-linked autocannon

Rotary cannons	80mm rotary cannon • GAU-53 • M2056 • T261 Lucifer

Miscellaneous	120mm ventral gun

Automated turrets

Ground installations	M5 Talos base turret • Scythe (M71 • M85) • M3045 • M3063 • M8 Wolf Spider

Point-defense guns	Arena (Mark 57) • Bulwark (M710) • Fortress (M965) • Goalkeeper (M606) • Helix (M810) • Rampart

Naval autocannons	11A2R1 • Breakwater • LNT-450 • Castor • Sentry • Spitfire

Mass drivers	Onagers (Mark 2488 • Mark 2551) • Ballista

Gauss cannon	M65 • M68 • M68B • M70 • M90A • M92

Railguns	M66 light railgun • M98 light railgun • Mark 2547/35cm heavy railgun • Mark 2555/20cm heavy railgun