MA5C assault rifle

Rate of Fire     : High, fully automatic, 15 rounds per second (RPS is unconfirmed). Operation        : Gas System. Fire mode        : Automatic. Accuracy         : Moderate to Good. Magazine Size    : 32 rounds. Maximum Ammo     : 160 rounds (including fully loaded magazine) Ammo Type        : 7.62 MM

The MA5C Assault rifle is a new version of the MA5B Assault Rifle seen in Halo 1, and will be the new default weapon in Halo 3. Its retooling makes it a much more accurate and deadly weapon than its predecessor at the cost of a smaller, 32 round magazine. It uses the same style of on-board computer system as the MA5B to provide the user with an active ammo counter and a digital compass for navigation. The MA5C does the same amount of damage in-game for headshots as bodyshots (meaning that performing consecutive headshots will not grant an advantage in multiplayer), and the weapon is not dual wieldable. This new weapon can be seen in the Halo 3 trailer.

Theories
It is thought the MA5C uses 7.62 Magnum rounds, instead of standard size. The reduced magazine may indicate more damage, and the MA series or any firearm series cannot convert into other ammo types, only to the extent of magnum sizes and shredder rounds. With the longer barrel, the rounds can be more utilized, seeing as how Magnum bullets have more gun powder equaling a higher voloctiy, adding the longer barrel will optimize range. The connection between the M6C Magnum and MA5C is the C, which may indicate it as magnum rounds for the Assault Rifle's side.

More likely, the C designation is merely to differentiate it from other weapons of the series such as the MA5B. rather than firing magnum rounds, it will likely make use of the 7.62x51mm Full Metal Jacket-Armor Piercing (FMJ-AP) ammunition used in Halo 1, or the 7.62x51mm Shredder rounds mentioned in the books, said to be interchangable with each other.