Kilo45-thanks for the directions.
As for mm vs inches, isn't a .30 caliber bullet the same width as the 7.62 mm? A 20mm shell must have been just over an inch in diameter? Unrelated, but one show on the Discovery Wings Channel features the Soviet "Frogfoot" SU-25, which flew in the 80's. A short video showed a small cannon (23mm?) firing straight into the metal below the cockpit canopy, with the pieces flying out like a dirt clod, but no apparent penetration through the metal.
Back to WW2-did the Spitfire, Hurricane etc .303 ever fire any incendiary rounds? Or did any normal bullets have magnesium tips, as with some US fighters such as the P-47, in order to better show where the impacts were?