These used the same projectiles as the 20x138B for the Flak 30/38 right? They don’t seem to be included in the Anderhub book on the x138B.
No, the Madsen did not use the exact same projectiles as the 20x138B Rheinmetall. The Madsen driving bands are 0.2mm smaller in diameter. For the same reason Madsen projectiles were also marked as such.