An upgrade of the Heavyarms to make it worthy for space combat. Besides a new dark blue-green color scheme, the Heavyarms Custom also sports two more chest gatling guns, and uses a pair of double gatling guns as its main weapon. In the Glory of the Losers manga, thrusters are added to the central part of the backpack and the rear skirt armor.
In A.C. 195, the Heavyarms Custom was used by Trowa Barton, while teamed up with the other four Gundam pilots, against the White Fang during the Eve Wars. The summer of the next year, Trowa piloted the Gundam Heavyarms Custom against Perfect Peace People forces. First in a battle against OZ-04MD Virgo IIIs on the Moon, then at the mobile doll production facility, Vulkanus.
In the December of A.C. 196, Trowa sent the Gundam Heavyarms Custom over to Quatre Raberba Winner to be destroyed by sending them into the Sun on the Vulkanus. When he came to realize that the Barton Foundation was planning to carry out the original Operation Meteor, he infiltrated the Mariemaia Army and was made to pilot a MMS-01 Serpent. Meanwhile, Quatre succeeded in a dangerous mission to catch up to the Vulkanus and returned it to Earth.