This Cannon entry in the weapon data represents an anti-aircraft style gun rather than something you buy at Ammu-Nation, so there is no price recorded for it. Its datamined figures are 30 damage, a fast fire rate of about 1500 rounds per minute, a range figure of 300 and a clip of 750. Numbers like these describe a mounted, rapid firing gun rather than something you carry and aim by hand. The 750 round clip and the 1500 rounds per minute fire rate point to a turret or emplacement weapon built to fill the air with fire, the kind of gun that appears on military bases and around restricted airspace rather than in a soldier's hands. The name in the data ties it to air defense, which fits a weapon meant to bring down aircraft rather than fight infantry. You will not find this version on any store shelf and there is no unlock condition to chase. It exists in the weapon data because the game needs stats for every gun it places in the world, including the ones mounted to structures rather than handed to players.
Pick it up in the world or buy it from Ammu-Nation.
The community companion for Grand Theft Auto VI. Database, maps, guides and tools for Vice City and the state of Leonida.