Whether employed against airborne quarry in an aerial combat or in strafing runs directed against "soft" ground-based targets, this single six-barrel rotary cannon delivers highly destructive bursts of 20-mm semi-armor-piercing high-explosive incendiary (SAPHEI) fire. Armor penetration is 45 mm at 500 m and 31 mm at 1 km. Mounted internally in the aircraft's nose directly in front of the cockpit windshield, it is the only permanently attached weapon system in the F/A-18.
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The gun's 578 M50 series 20-mm PGU-28/B rounds are stowed in a cylindrical ammunition drum just aft of the radar set, be it the APG-65 or the newer APG-73 (the latter is found in the Super Hornet-E/Fs, retrofitted U.S. aircraft and later production C/Ds sold to, for example, the Finnish, Malaysian and Swiss air forces). The drum, coupled with the barrels and breach above it, forms a single modular unit, which is hydraulically driven and electrically controlled. The feed system is rotary linkless, double-ended.
