So, I think that the Typhoons 20mm would have been able to destroy any German tank up to the Pz.Kpfw IV. After that rockets, or lucky hits would have been needed. There would still be the possibility of destruction up to the Pz.kpfw V Ausf A.
A quick internet check suggests that the Vickers S guns on the Hurrican were fed by a 15 round drum. I also just learned that the Hurricane was the first Allied aircaft to use rockets.
It does make for a nice size load. The Ju-87G carried 12 rounds to each 37mm gun, the Il-2 had 32 rpg (I believe), and the P-63 King Cobra carried a very impressive 58 rounds for its 37mm cannon.