Mark 2551 Onager

The Mark 2551/25cm Portable Magnetic Accelerator Cannon is an upgraded variant of the Mark 2488 Magnetic Accelerator Cannon (also known as the "Onager") developed by the Misriah Armory following the end of the first Human-Covenant War. It uses a 25cm ferric-tungsten depleted uranium round that is fired at supersonic speeds.

Service history
The UNSC's postwar prototype flagship,, is equipped with a number of Mark 2551 MAC dorsal turrets. During the initial skirmishes on the Forerunner shield world Requiem in 2557, these turrets were used to fend off the Didact's Cryptum, forcing the Didact to retreat. ONI's Ivanoff Station near Installation 03 made use of several automated Mk. 2551 Onagers for defense against space debris and later against several Covenant CRS-class light cruisers when the station was attacked by Covenant forces under the command of the Didact himself.

List of appearances

 * Halo 4