Sorry to nitpick, but isn't the purpose of this sub-forum?
- On Bf 109 E-3 and later Emil versions with MG/FF guns, empty cartridges of 20mm ammos were not ejected to the outside through the underwing gun port but remained inside the wing and were removed by hand after the flight via a rounded hatch.
(This slot was the ejection port for the wing MG 17 used on Bf 109 E-1).