While popular with some ACAMs (Arm Chair Air Marshal) the 40mm guns were lousy for air to air and not that great against surface targets. They used the same ammo as the British 2pdr pom pom AA gun, much less powerful than the 2pdr AT gun or the 40mm Bofors gun. The Vickers gun fired at about 100rpm and weighed over twice what a Hispano gun did.
The RR gun was trialed in aircraft but just about all of the production was used on MGB, motor minesweepers and harbor defense craft and in this application there was no magazine., the gun was manually loaded for each shot.
What an interesting point!
I went off and did some background reading. I had always assumed that the Vickers S was a purpose designed anti tank weapon - and had no idea that it was basically a warmed over COW gun, firing a modified shell from a modified pom-pom cartridge. A simple comparison between its 1,870 ft/s velocity and that of the purpose designed Bordkanone 3,7 firing at between 3,800–2,600 ft/s, shows something of a gulf in performance, eh? No wonder the S was quickly phased out once Panthers and Tigers started to appear.
However, that said, I had no idea that cannon armed (and comprehensively armoured!) Hurricane mk ivs, carried on operations right the way through the war in the Far East. That in itself answers a question I had regarding the point of the 'universal wing' for the Hurricane! Its seems that not facing heavily armoured tanks in the Middle East, the fact that its HE shells were particularly accurate, appear to have offset its other disadvantages. The accuracy of guns as opposed to RPs has also caused some other synapses to fire; I watched a very interesting vid on Youtube which featured some first hand accounts from Mosquito Tsetse pilots who were extoling the merits of the 57mm Molins gun. Might be cause for a separate thread there, methinks - lots of interesting things to unpick.