Thanks for that Bruce. I'm grateful. Many years ago (as a teenager & in my twenties, so it's ages ago!) I used to be quite a keen collector of both 303 & 7.92mm cartridges. Somewhere in the dark recesses of my loft I think I still have copies of both '.303 Inch' by the late Peter Labbett, & '7.92mm' (not sure if that's the exact title of the latter) by Daniel Kent. I think I'll try to dig them out & see if there's anything in them specifically relating to this topic. It's proving quite fascinating.