During development, the XF4U I THINK mounted twin .50s in the nose and a pair of .30s in each wing. However the Americans learned from reports by the RAF at the Battle of Britain that the .30s were insufficient for modern aircraft armament, so the cowl guns were moved to the wings (and in their place was an enlarged main fuel tank) and the four .30s were removed from the wings. Initially they replaced each pair of .30s with a single .50 cal (for a total of four Browning M2s) but BEFORE the aircraft was adopted into full production the armament was further increased to the six Brownings.
So yes, the evolution of the F4Us armament DID at one point include four .50 cal, but this was changed before the aircraft ever entered production, and as AFAIK, excluding the cannon-armed 1C, 4B and later models, no regular-production Corsair carried fewer than the usual US "six-pack."