The M84 heavy machine gun was a recoil-operated, belt-fed, fully automatic heavy machine gun in service with the UNSC Army and Marine Corps between 2588 and 2680. Chambered for the 12.7x99mm (.50 BMG) cartridge, the M84 provided UNSC forces with superior range, accuracy and terminal effects compared to machine guns and automatic rifles chambered in smaller calibres, at the expense of increased weight and reduced portability. This increase in mass meant that only personnel using powered armour or exoskeletons could fire the weapon without a mount of some sort; combined with its high damage characteristics, this resulted in the M84's extensive use mounted to vehicles and aircraft. The machine gun was produced in two variants; the M84 A1 had a conventional layout and an integral heavy bipod,