While I can't help with specifics, I can contribute some generalizations. I helped write the battle damage repair manuals for two different aircraft programs. That gave me an opportunity to research a lot of background stuff, plus talk to test engineers. As I was an aircraft history buff, I bounced what I learned against what I read about WW2 aircraft.
Baff is pretty close to approximating what happened in the BoB by giving bomber pilots extra protection. Towards the end of the BoB, the Luftwaffe had installed field mods that improved protection for pilots and systems, making them hard to shoot down with .303cal bullets. Unlike a 12.7mm/.50cal round, a .303cal round just did not store enough energy to fatally damage primary aircraft structure. Obviously .303cal bullets could degrade primary structure to the point of failure, but it required A LOT of them concentrated in one location.
Put another way, it only took a few 12.7/.50cal bullets to inflict the same damage caused by a dozen .303cal bullets. Plus, most pilot armor could resist all rifle caliber bullets and nearly all cannon shells.
The RAF had already figured that out by 1940, which is why it was combat testing small numbers of cannon armed fighters during the BoB.