Sorry guys it is not my intention to botch the party, but twenty one 2cm hits sounds a bit like a taste of hollywood there.
While a full load of 7.92mm bullets might certainly not be enough to bring down a sturdy P-47, the alleged amount of 2cm shells absorbed by this gentleman´s Thunderbolt is far beyond the realms of reality.
The photos posted here, even while showing important damage, are clearly not the product of taking 21 of the 2 cm shells. I have seen Bf 109s with that sort of damage that made it back to base.
Some of the hits shown on the photos certainly come from 2cm shells but never to be 21, and he was lucky they did not hit the engine: a sole well placed 2cm shell on the engine of even the P-47 is a sure kill.
The Fw190As and the P-47s are surely the sturdiest and greatest damage absorbers of the war. Both had radial engines, while P-51, Bf109, Spitfires and Lightnings had liquid cooled engines and could not take very great damage.
German interceptos in many cases used 1/10 of the rounds Johnson´s P-47 allegedly took that day to shoot down a four engined heavy bomber such as the B-17 and B-24, which of course are heavier and far harder to destroy.
The P-47 if indeed capable of taking important damage did not demand, being generous, even 1/4 of the rounds you are saying he took that particular day.