Gilles, I managed to find enough in Holland (16) to outfit one side of my limber for display. Now having said that, I had a 37MM Bofors anti tank gun and for it I used steel casings that were made up in a machine shop. I used the bottom of a shot gun shell with the primer to fire the casing. Rifle powder and black powder will make an impressive bang and flash. Be careful though with the steel blanks as they aren't as forgiving as the brass and a little extra powder will swell them up so bad they are almost impossible to remove from the breech.
Ask me how I know.
Cheers,
Barry