The RX-77 Guncannon is a fictional mobile suit from Mobile Suit Gundam anime series, originally designed and illustrated by Kunio Okawara. One of earliest mecha designs in the Real Robot genre, Guncannon's concept of a heavily armored humanoid machine with dual shoulder cannon became the inspiration for various artillery fire-support mecha in other mecha anime and games. The Dankof from Blue Comet SPT Layzner (1985), Dragonar-2 from Metal Armor Dragonar (1987), Schutzwald from the Super Robot Taisen: Original Generation video game series, and other designs owe to the aesthetic of the Guncannon as inspiration for their designs.
The Guncannon was a step up from the RX-75 Guntank; while the Guntank was more a "tank" than a humanoid robot, the Guncannon was a true mobile suit with limbs. However, it did share the Core Block System, using the same FF-X7 Core Fighter. This allowed the Guncannon's pilot to quickly change control with Guntank and RX-78 Gundam.
The first Guncannon was the prototype RX-77-1A Guncannon A, which had poor mobility due to its heavy armor. The second version, RX-77-2 Guncannon, corrected this problem. As defensive weapons, it mounted two 60mm Vulcan guns in the head. However, the Guncannon's primary weapons were the twin 240mm cannons mounted on the shoulders, which were used for the mobile suit's design purpose: mid-range fire support. The Guncannon was also armed with a high-precision beam rifle for sniping operation, being one of the first mobile suit equipped with a beam weapon.
The Guncannon was less mobile but more heavily armored than its cousin, the Gundam. This allowed the Guncannon to be a significant threat to Zeon's Zakus. Unfortunately, the extra armor provided no additional protection against the powerful beam weapons, and heavy projectile weapons (such as the Giant Bazooka used by MS-09R Rick Dom) were also capable of causing severe damage. It also lacked any sort of melee weapon, rendering it having to fight empty-handed during close encounters with an enemy unit. Another disadvantage was that its 240mm cannons only held 20 rounds per cannon, limiting the Guncannon's effective operation time on the battlefield.
During the Zeon attack on Side 7, only one RX-77-2 survived the attack. It was later stationed aboard the Pegasus-class assault carrier White Base and assigned to Kai Shiden. However, when White Base made its way to Jaburo, another Guncannon was transferred to the White Base to replace the space-incompatible RX-75-4 Guntank piloted by Hayato Kobayashi. To separate the two units, they were named the "C-108" and "C-109" respectively. Both units were heavily damaged at the final battle of the One Year War at the Zeon's space fortress A Baoa Qu. Kai's Guncannon later reappears in Hayato's mobile suit museum in Zeta Gundam.
The RX-77-2 Guncannon was the only Project V mobile suit ever to have limited mass-production. It served as a main mobile suit until the Federation introduced the RGM-79 GM; however, due to the high cost of beam weapons, many Guncannon units were armed with conventional machine guns or rifles. Some unlucky pilots were not issued a hand weapon at all, and had to rely on the Guncannon's built-in armaments. In the Gundam 0079: Zeonic Front video game, a three-man Guncannon squad was commanded by young, brash Federation pilot, Lieutenant Agar (who would later become pilot of the RX-78-6 Mudrock Gundam). This team would pursue the infamous "Midnight Fenrir" Zeon special operation mobile suit team up to the Battle of Jaburo. Also in Cross Dimension 0079 video game, at least two Guncannons was used by Albatross transportation team in the Gobi Desert, though game's dialogue said they already loss several units. There were also reports of several Guncannons used to assist the 16th Autonomous Corps, the Thoroughbred as well as at least 1 Guncannon used to assist Yuu Kajima during the final days of the Blue Destiny units' test.
The manga Mobile Suit Gundam: The Origin features a Guncannon in the same role as the Guncannon in the original series. Like other designs from the original Gundam series, it received a slight makeover by Kunio Okawara; the barrels of its shoulder cannons are longer and there are only 3 fingers on each hand.
As the One Year War came to a close, the Federation began plans to mass produce the other machines of Project V. The RX-77D Guncannon Mass-production Type did away with the Core Block System and used the more economical titanium/ceramic composite armor instead of lunar titanium to cut costs. In addition, it possessed additional verniers and thrusters, making it even more powerful and maneuverable than the older model. However, this revision was never produced as planned, with only a few suits being distributed to units such as the Pegusus carrier Gray Phantom and the White Dingo team in Australia.
The F71 G-cannon has two other variants. One, the VSBR Type sports two shoulder-mounted variable-speed beam rifles instead of machine cannons. The other variant, the Full Equipment Type, packs even more firepower in the form of missiles, cannons and other weapons.