Magnetic Accelerator Cannon
From Halopedia, the Halo wiki
Summary
The Magnetic Accelerator Cannon or MAC gun is the standard main weapon of all UNSC cruisers. It uses huge magnets that condense a molten sphere of super heated ferric-tungsten projectiles, and fires it at near-light speed. The damage it inflicts it tremendous, though reloading takes quite awhile. A more effcient, experimental model of the MAC gun, which can fire three rounds before reloading, was mounted on the Pillar of Autumn. Super MAC guns are loaded on the defense platforms orbiting Reach, Earth, and other strategic locations that must be protected, and are much more powerful than normal MAC cannons.
