Well, maybe I have to expand my theory a little.
Most kills are the result of shooting off the tail or wing and the plane tumbles to Earth. If the pilot bails or the plane hits the ground, kills and assists are awarded based on the number of hits. On those rare occasions the pilot is killed while in flight, the kill is awarded to the person who did the killing. So no matter how much damage you do to the enemy, if someone shows up and puts a single round through the pilot's head, he will get the kill.
Don, on your field ack example, the rule of who has the most hits gets the kill is still valid. The P-38 puts two rounds in; you hit him once with the field ack and take the wing off; and the P-38 gets the kill and you the assist. I had an incident in a field gun where an enemy P-51 was being chased by at least three others and I can only assume they where getting some hits. I fired from the field gun and one of the rounds landed on the 51's windshield. The plane exploded a second latter and I was awarded the kill. So the theory of who kills the pilot gets the kill seems to hold.
So shoot at the pilot, not the plane.
MachNix