At the end of the First Robotech War, the GU-11 reigned supreme. The REF supreme command wanted to phase out this older weapon which could only be used by the older Valkyrie series for the newer smaller GU-XX series gun pods which would be used on the newer Alpha and Beta fighters. To many of the supreme command's dismay, a large portion of the veterans from the first Robotech War expressed their desire to continue to fly the older VF-1's over the newer designs. REF supreme command decided to keep the older veritecs flying but upgrade the avionics and weapon packages. Thus the GU-111 project was born headed by General John Adkins (REF).
In all outward respects the GU-111 is identical to its original cousin. As a result any mecha which could use the massive GU-11 could also use the GU-111. However internally there are sizable differences. Using new materials, researches were able to make a lighter higher caliber weapon which could fire 65mm caseless ammunition at 700 rounds a minute. The weapon was popular with the veterans of the First Robotech war, although younger pilots tended to continue to use the GU-XX series gunpods.