Although the RCX-76-02 Guncannon First Type was defeated by Principality of Zeon's mobile suits in the Battle of Mare Smythii, cannon-type mobile suits were found useful as a intermediate-range support and development continued after the battle. The GM Cannon was equipped with a 360mm rocket cannon and was deployed in the North American and the African fronts. A portion of the GM Cannons were sent into space and were improved into the space assault type RGC-80S. The split leg armor which had been mounted as a counterweight for the 360mm rocket cannon was removed, and the suit was fitted with the RGM-79SC GM Sniper Custom's leg sub-thrusters instead. Units assigned to the 142nd MS Team, a mobile suit cover team for the Revil fleet, had a unique blue and white paint scheme, rather than the standard red and white.
360mm Rocket Cannon
Beam Spray Gun
Balzac-type 380mm Rocket Bazooka
Developed as a new optional equipment for the GM series, this weapon was designed for space combat, and has a focus on increased production efficiency.
According to records, the GM Cannon Space Assault Type participated in the attack on A Baoa Qu during Operation Star One.