Developed sometime after U.C. 0100 as part of a next generation mainline mobile suit development plan, the RXR-44 Guntank was one of the many prototype mobile suits proposed to the Earth Federation Forces. It was not formally adopted and was abandoned after testing, only to be acquired by Roy Jung, a formal brigadier general of the EFF. Roy named the mobile suit "R-44", with R being his initial and 44 being his age when he acquired it.
After acquiring the mobile suit, Roy displayed it at his military museum in Side 4's Frontier IV colony.[1] When the Crossbone Vanguard attacked the colony in U.C. 0123, Roy attempted to fight the invaders using the Guntank R-44, which was already more than ten years old by that point. However, the mobile suit's lack of maintenance soon showed: Its hatch was unable to close, and its left cannon suffered a barrel burst after a single shot. Soon after, a Den'an Gei destroyed the right cannon with its beam saber, killing Roy.