From Halopedia, the Halo wiki
The Individual Combat Weapon System series (ICWS series), MA line, MA Assault Rifle series or MA series is a line small arms produced by Misriah Armory. It is the oldest rifle in use with the United Nations Space Command and is in use with every branch and division of the UEG's armed forces. Weapons of the ICWS series are given the prefix "MA".
MA series weapons are gas-operated, air-cooled, and utilize a rotating bolt. They are magazine-fed and commonly cambered in the 7.62×51mm round, with specialist ammunition available via request. Fire modes include single shot, burst, and fully automatic. They are easy to clean and use.
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