There is very little info on the 8mm Ultra, all of which is duplicated on various websites. The consensus info is that it was a Gustaf Genschow & Co. development around 1934 for a Walther PP in order to provide an intermediate powered cartridge between the 7.65 Browning and the 9mm Luger. It was not succesful and was made only in limited quantities. Cartridge is relatively rare today. (Erlmeier, Brandt Ref. 109).
