The Magnetic Accelerator Cannon, or MAC, is the primary weapon mounted on UNSC combat ships.
Enormous coilguns, they accelerate a depleted uranium or tungsten slug to a fraction of the speed of light to physically punch through everything from energy shielding to Forerunner armor plating.
The advent of these enormous cannons forever changed combat in space for the UNSC, giving their state-of-the-art ships a massive firepower and range advantage over the smaller craft that were often appropriated by pirates and the Insurrectionists. They require a lot of power from the ship's power plant and take up a large portion of the ship's prow, and can drive solid slugs through even the most heavily armored ships.
With the start of the Human-Covenant War, MACs proved to be one of the UNSC's strongest weapons for dealing with the enemy's shielding technology, hitting with such force as to severely drain or even overload the shields and expose the hull to attacks with missiles. "Super" MACs mounted on orbital defense platforms could eliminate enemy shields altogether and critically damage Covenant ships, making attacks on a proper defense grid very costly.
Magnetic Accelerator Cannons are the UNSC's primary weapon, mounted on almost every ship larger than fighters. Long-ranged and heavy-hitting, they operate as the key strength in the UNSC's alpha-strike tactics but have a long cooldown. This weapon's Covenant counterpart is the weaker but more rapid-fire Plasma Torpedo.
These weapons come in all sizes and strengths from the incredibly light and weak MAC onboard a Gladius-class corvette to the enormous, powerful MACs onboard the Infinity-class supercarrier. They are mounted in varying numbers on different ships; frigates mount a single MAC, destroyers and most cruisers mount two, the Phoenix-class refit fields three, and the Infinity mounts four.
The "Super" MACs installed on the UNSC's orbital defense platforms have the most rapid fire rate while still having some of the best damage per shot of all MACs. The twin guns aboard the Viery-class orbital defense platform, which fire sequentially, can have their fire rate even further bolstered by the presence of a nearby Anchor-class station with a Microwave Generator upgrade, making them some of the most feared weapons in the Covenant's eyes without some means to attack from out of range.
If choosing Admiral Stanforth as the fleet's admiralty, the UNSC gains access to top-of-the-line technology such as the Point Blank-class's "Jester Rounds" which knock out a ship's weapons, engines, and slipspace drives, leaving them dead in the water for a short time, or the "Trojan MAC" aboard the Thanatos-class, which completely bypasses enemy shields altogether.