Sorry to revive such an old thread, but I stumbled across it while searching for information about the 20mm Inglis cannon, an example of which I spotted on a recent visit to the National Firearms Centre in Leeds, UK.
The information in this thread is very useful, but if anyone has more details of the gun, I would like to receive them.
For interest, shown below is a photo from the Ammo Photo Gallery on my website of some (not all) of the 20mm cannon rounds in service up to 1945. The Hispano aircraft cannon round is the 20x110 shown on the far right; the Oerlikon S is the 20x110RB next to it. As you can see, they are very similar but are definitely not interchangeable. Incidentally, both rounds are still in production to this day (those guns last a long time!).
You need to be careful in discussing 20mm Oerlikons as these came in various sizes. The Type S shown here was the biggest and most powerful of the WW2 versions and was used almost exclusively in AA guns, but there were also less powerful ones used in aircraft cannon: the 20x101RB (Type L, used mainly by the Japanese Navy in WW2 in the Type 99-2) and the 20x72RB Type F (used by Japan in the Type 99-1). The Luftwaffe used a variation of the Type F firing the 20x80RB ammo shown.
The postwar 20x128 Oerlikon is much bigger and more powerful.
