I don’t think that worked as well as reported. The velocity of a .50 BMG wouldn’t allow a lead bullet covered in copper the ability to bounce like that and then penetrate the steel plating.
I understood our pilots aimed for the relatively thin plating over the engine compartment.
I don’t know about the .50 BMG being used today but I sliced open several .50 cal bullets from the WWII era. There was not a bit of lead in them. The brass shell surrounded a stainless steel core. Awesome little things.