Great work as always Sir Ron of Ol Kentucky. I won't be much help to the 400 Hammer cause other than to say I do believe you are on the right track to get to where you designed you wanted to to. That will be as close to "One bullet for all" as one bullet can be. Of course this "One bullet" is being launched by the One True 458 WM the Magnificent which makes any bullet just a little bit better.
Side thought as a question; How does bullet against Steel tests show us how bullet on Elephant heads work? I have never thought steel showed us much about bullets except how that bullet works on that steel so eager to learn.