It wasn't at the tank town Pyro, but it was near a normal airfield town.
The situation was;
I saw a medum alt Ju88 formation come in to bomb the town. I was flying a Bf109K-4, and noticed the Ju88 pilot was not very aware of enemy attacks. I felt lucky because I can save some ammo, crept up behind the Ju88 lead buff, aimed for the right wingroot and closed in to 400 yards. Then I began tapping on the secondary fire button to save 30mm ammo.
I only saw normal sprites and was momentarily confused what was going on, so I just held the cannon fire button down in panic, and after some more shots going in I finally saw a 30mm explosion effect.
This is what happened to me.