 The "GunVal Project", seven F-86s and five veteran pilots, was attached to the squadron to test armament modifications in combat.North American Aviation removed the six M3 .50-caliber machine guns from four late-production F-86Es and six block-one F-86Fs, expanded the size of the gun bays, strengthened the surrounding frame assemblies, and mounted four newly developed T-160 20mm cannon in their place.Having a similar rate of fire, the cannons were expected to significantly increase the Sabre's lethality over that of the machine guns, whose armor-piercing incendiary ammunition was usually ineffective against jet aircraft above 35,000 feet of altitude.