I remove this paragraph because there is a lot of controversion in the net about this. Maybe some1 has sources about this thing.
Fighter Command Campaign Diary, 10 July 1940:
Quote:
Air Intelligence Reports
Inspection of an Me109 which was shot down recently, confirmed that this aircraft is armed with 2 cannon, 1 in each wing, and 2 machine guns firing through the airscrew [propeller]. Previous reports that this aircraft carried 3 cannon are incorrect.