just also think about the shot cadenz... the flakguns were maybe not the biggest when it came to caliber - esspecially compare to the 105mm of the IX-boat's DG...
but the "small" 20mm let off a mass of bullet within a time... :hmm:
my brother once used his small caliber rifle (.22 Hornet) on a 10mm steelbar just to test his new bullets (hunter, making his own ammo/cardridges with special bullets for maximum efficiency on this and that game) and though it was not a full metal jacket bullet but meant to spread/collapse quickly and release the energy very quick - it went through the 10mm of steel like a hot knife through butter
Now imagine a 20mm flak gun firing with a high frequenzy :hmm:
It has to do at least "some" damage somewhere...
and now just let a bullet hit a fuel tank....
