I would think that makes the point about original usage quite well. You must handload the .405 to achieve what the .450/400 does. To make it work out best might also require a different rifling twist and a longer chamber than the 405 was originally designed for. If you want that type of performance why not just chamber the rifle in a round that was originally designed to produce it? I'm not knocking the .405, but if you want .450-400 performance you could chamber for .450-400, use factory ammunition, and still handload to your heart's content.