F-106 retrofitted with a cannon. Convair in 1972 proposal to endow the F-106 with a 20-mm internal M61A1 rotary gun with 650 shots in what became known as Project Six Shooter. The rotating gun was mounted inside the rear half of the weapons compartment, replacing the Genie nuclear warhead rocket. However, the four AIM-4F / G Super Falcon missiles could still be loaded. The F-106A equipped with the cannon could be distinguished by a flared fairing under the fuselage, which provided space for the rotating barrels of the cannon. The six-shooter program also included replacing the cockpit cover with a "transparent top", which eliminated the metal strip above the pilot's head, greatly improving the visibility of the cockpit.