Technology & Combat Characteristics
The GM Cannon (Thunderbolt Ver.) is one of the mid-range support mobile suits deployed by the Earth Federation Forces. It shares about 60% of its parts with the RGM-79 GM (Thunderbolt Ver.) and uses the same handheld armament. The GM Cannon (Thunderbolt Ver.) has a large backpack with a rocket cannon mounted on the right and a sub arm on the left. This large backpack is a modified version of the one used by GM (Thunderbolt Ver.) and can be purged when needed. The mobile suit also added thrusters on its calves, which are utilized to counteract the recoil of the rocket cannon, and added targeting sensor on the right shoulder, above the chest.
History
The Moore Brotherhood's flagship, Beehive, was supplied with the Full Armor Gundam, Guncannons, Balls, GM Cannons, student volunteer pilots and ammunition for the final battle in Side 4. Used by the student volunteers and pilots of the Beehive, the GM Cannons and other mobile suits were used in a diversion tactic (rather controversially) to outnumber the Living Dead Division's snipers and overwhelm them so the Full Armor Gundam could sink the main fleet.
Although the novice pilots were no match for the snipers, they managed to take out a few snipers through sheer numbers. They were engaged by Fisher Ness in his Rick Dom who took out at least one Ball and 3 GM Cannons. Although unknown to the pilot of a Guncannon (the last surviving member of the squadron), the MS-06R Zaku II High Mobility Type (Reuse "P" Device) had mopped up all of the MS deployed, and the GM Cannons were completely decimated.
Later, a few GM Cannons were seen battling Zeon's main fleet and subsequently guarding the Dried Fish after it was captured by the Federation Forces. One GM Cannon played a major role in stopping the captured from blowing up the ship. When the Federation surrendered to Zeon, the GM Cannons were used to transport Federation and Zeon soldiers to a Chivvay-class. It is unknown what happened to the GM Cannons after this event.
After the One Year War, many GM Cannons were deployed as part of Konpei Island's defense fleet alongside RGM-79 GMs and Balls to intercept the approaching South Seas Alliance forces and their Psycho Zaku Mk-IIs.