From Halopedia, the Halo wiki
The M343A2 Minigun is a heavy machine gun in use by the United Nations Space Command after the Human-Covenant War. It is a successor to the M41 and M46 machine guns, with which it shares the erroneous "chaingun" moniker.
The M343A2 is an electrically driven, five-barreled Gatling-style machine gun that is compatible with all standard UNSC heavy weapon mounts. The M343A2 is often installed on a pneumatic full-rotation turret as the primary armament of the M12B Warthog, and is also available in a semi-portable tripod configuration for site defense. The latter configuration has a much shorter barrel assembly.
The M343A2's lethality is comparable to that of its predecessors. Barrel wear is considerably diminished in comparison, though the weapon will overheat after periods of sustained fire. Although the M343A2 is designed to use the latest polymer-cased and energetic propellant rounds, UNSC units have been ordered to deplete existing stocks of older ammunition before transitioning to newer cartridges. As opposed to its predecessors, the M343A2 ejects its spent casings from the left side.
Carrying the turret decreases the player's speed and maneuverability as in previous titles. However, it should be noted that this actually renders the player invisible on the motion tracker unless the weapon is fired, making the M343A2 useful for catching the enemy off-guard while on defense. The M343A2 kills Spartans in 12 rounds in War Games. It is ranked a Common REQ in Warzone simulations, and is available at Level 2 energy while giving 50 REQ points if sold.
The weapon's designation is an obvious reference to 343 Industries.
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