Test 30mm offline, K4 vs B17. Saddle up at 200 and single shot 30mm into an inboard (engine\wing root). Count shots until the B17 looses the wing or blows up. Best case for the 30mm is 5 rounds to put a heavy bomber out of action in data from Rechlin. I can never find specifics for this in terms of impact location(s). Just the assertion from testing and pilots that 5 rounds is the average. But, we have many ww2 photos of allied bombers after landing with horrendous damage from flak and cannon fire.