The Heavyarms suits were designed in 1995 by Kunio Okawara, along with many of the other mobile suits appearing in the anime. Heavyarms Kai, along with the other four 'second-stage' Gundams, were later redesigned by Hajime Katoki for the 1997 OVA Gundam Wing: Endless Waltz. The new design is now canonical. Retcon designs for Heavyarms, along with the other four original Gundams were also created, which were published in Newtype magazine.
Gundam Heavyarms is one of the five mobile suits sent to Earth as part of Operation Meteor; a plan whereby rebels would be able to weaken the controlling influence the United Earth Sphere Alliance and the Organization of the Zodiac (OZ) held over the orbital colonies. Heavyarms was designed by the Barton Foundation in the cluster of orbital colonies located at the L3 Lagrange point, and was to be piloted by Trowa Barton. As seen in the Endless Waltz OVA, Trowa was killed prior to launch, and his role (and name) were taken on by a nameless mechanic.
Heavyarms' first major appearance is in Episode 3 of the Gundam Wing anime, and is piloted by "Trowa Barton" until Episode 17, at which point the Gundam is abandoned so "Trowa" can travel into space and infiltrate OZ. The Gundam is recovered by Sally Po at a point prior to Episode 41, who helps deliver it into space.
Heavyarms cannot function in space, so is upgraded to the Heavyarms Kai design, and is involved heavily in the fighting leading up to the conclusion of the series. Heavyarms is used in the manga set between Gundam Wing and Endless Waltz, and at a point prior to the OVA, is sent to Quatre Winner for disposal along with three other Gundams.
During the events of Endless Waltz, the sun-bound satellite carrying four Gundams must be recovered. "Trowa" and Heavyarms are reunited during the third episode of the OVA, and the Gundam is used during the battle against the Mariemeia Army in Brussels. At the end of the OVA, Heavyarms is destroyed by self-detonation.
Heavyarms holds the distinction of being the only Gundam to have survived the events of Gundam Wing relatively intact; it was not completely destroyed until Endless Waltz, and the design upgrade did not require a complete rebuild of the mobile suit.
Shortly before the events concluding the Gundam Wing anime, the Romefeller Foundation used data from the five Gundams to design new mass-production mobile suits. Derringer Arms was based on the Heavyarms Custom, with a decreased range of weapons and equipment.
An unknown number of Derringer Arms units were produced at Romefeller's secret manufacturing plant on Colony X18722. Former OZ pilot Trinoi Levinski stole a Derringer Arms during Tiel Nonbleu's break-in at the plant, using it to escape the colony. Trinoi helped drive off the Romefeller pursuit force, allowing Tiel's group to reach their goal, the Graveyard of Soldiers. After arriving, Romefeller's Gundams appeared, ready to exterminate the "irregulars". In a bloody battle, Trinoi managed to destroy both of the enemy Gundams, but ended up dying himself when the critically damaged Derringer Arms exploded.
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