I know.
The problem was simply speed. Of course you can cut a wing by opening the "shower" using the gun. But it takes some time to achieve that, too much time to fly co-speed with the target.
History also proves that using explosive shells the fighter aircraft was endangered the same as the target. When it blew up the fighter blew up, too.
BTW I have downed a danish Starfighter without use of any weapon. The pilot made a safe silk let down. (parachute landing)