You dont know this cartridge! It's impossible to duplicate something with it! You have to use only the 347gr. bullet's caliber .423 ! The muzzel velocity is 680 m/s , not more ! There are not original load's for 400gr. bullet's for this cartridge and with modern powder's you can do nothing! If we need more power, we take a 404 Jeffery or a 416 Rigby, and we dont make experiment's! The first question was, who hunt with this cartridge,.... nobody !