Magnetic Accelerator Cannons, known colloquially as MAC guns, were the primary weapon system of most UNSC warships across the course of the human Covenant War and beyond. The weapon took the form of a large coil gun, which employed electromagnetic energy to accelerate a projectile to 4% the speed of light, resulting in the most powerful non-nuclear weapon system in human history. Starship mounted MAC guns utilized 9.1 meter long depleted uranium rounds, whereas defense platforms like Cairo Station use rounds comprised of ferric tungsten. A MAC gun size requires the weapon to be built into the superstructure of its parent ship or station, meaning that the entire craft was reorient itself in order to aim the cannon. This highly precise, unguided targeting is normally carried out by ship-board AIs, or dedicated tactical computers, as manually aiming the weapon would be close to impossible. The MAC's firing process employs electromagnetism to accelerate a projectile to extremely high velocities. A coil of conducting wire is charged with an enormous current, creating a powerful magnetic field, which attracts the metal shell. As the projectile passes through each loop of the highly charged conducting wire, the loop ahead of it is activated, further accelerating the projectile down the barrel of the coil gun. By the time the round has reached the weapon's muzzle, it is accelerated up to a maximum of 12,000 kilometers per second, creating a recoil effect so intense that the ship or station firing the weapon is forced to briefly burn its maneuvering thrusters at full strength in order to remain stationary. Where other weapon systems such as missiles and cannons are previously proven to be of limited effectiveness when engaging shielded covenant warships, the sheer power behind a single MAC round allowed the weapon to inflict serious damage on a target shield barrier, sometimes even forcing through it completely. When faced with an unshielded target, the effect of the MAC round is devastating, effortlessly tearing through whole plating and deck after deck of compartments. Almost always perforating the target vessel entirely, and emerging barely slowed from the far side. Though almost always mounted on space-faring craft or facilities, smaller and lower yield-max are occasionally installed on a planet's surface for the purpose of antiorbital defense. In such example, the MAC 2488 Onager used only 15cm ferric tungsten slugs, but the weapon was still capable of inflicting critical damage on a Covenant CCS class battle cruiser, as well as effortlessly tearing groups of phantom dropships to ribbons. The MAC 2488 was ultimately succeeded by the even more effective MAC 2551, which was installed not only on UNSC installations like Ivanov Research Station, but also on the UNSC Infinity. Though the smaller Onager Max provided the infinity with a powerful defensive weapon, they paling comparison to the MAC guns installed as the vessel's primary weapons. These series 8CR03 Super Max are several times more powerful than any previous Magnetic Accelerator Cannon, wielding sufficient firepower to create terrestrial craters several miles in diameter, and to puncture the hull of the Gargantuan Forerunner flagship, the Mantles Approach.