I still call BS. You are getting some phenomenal damage compared to what I see Bish guns do. 1 burst and planes explode. If my guns did that too, I might understand. Something ain't right.
It's just gunnery. A one-half second burst in a D9 puts out about twelve 20mm rounds... and the same burst in an LA-7 puts out about twenty 20mm rounds. If you're ~15% accurate (functionally where my accuracy currently is), that's two or three 20mm impacting your opponent every time you pull the trigger. If you're steady with your aim, those rounds will usually hit the same component and cause it to fail. And that's just a half-second burst.
Factor in longer bursts, cockpit hits, the additional damage that the machine guns in the D9 cause, etc., and you can easily do 14-18 kills in a D9 in a single sortie without rearming (I have one or two 14 kill sorties uploaded to my YouTube channel). An LA-7 can usually get 12 if everything is done optimally (I had a 12 kill sortie the night before in the LA-7). Even a mid-war Spit IX can get 10-12.
Most of my D9 sorties are landed because of run out of fuel, not ammo (and I usually take 100% fuel).
Also, you realize I was flying as a Bishop during the sortie in question, right?