Similar to how the failed FA-78-1 Gundam Full Armor Type was meant to enhance the offensive capabilities of the original RX-78-2 Gundam, the FXA-03 Full Armor pack for the Mk-II was meant to add greater offensive and defensive capabilities. The new armaments included one head-mounted Vulcan pod, Grenade Launchers on its forearm, and a 2-barrel Beam Cannon with an attached Grenade Launcher.
Although the Mk-II didn't mount the standard vulcan guns on the head, it is able to be outfitted with a 60mm 2-barrel vulcan pod on its head, capable of carrying a total of 1400 rounds. The vulcan guns are housed in the left side with two firing ports, while the right side functions as a balancer and magazine. This optional weapon was developed because installation space in the head unit could not be reserved for mounting the vulcan guns.
Two grenade launchers are built into the mobile suit's left forearm.
2-barrel Beam Cannon
Unlike the normal Mk-II which carried a beam rifle, the Full Armor Gundam Mk-II had a more powerful 2-barrel beam cannon attached to it's right forearm.
For extra firepower, another grenade launcher is built into the Beam Cannon.
While the Full Armor pack did increase the Mk-II's offensive and defensive capabilities, the FXA-05D G-Defenser however had a more well rounded armament and did not weigh down the Mk-II in combat, so development was focused towards the G-Defenser and the Full Armor pack was never used.