And just to muddy the waters even further, if the original 310 grain load (S.D. of .346) at 2,000 fps in the 400/350 Rigby was no different, at least in Taylor's opinion, from a .375 H&H load using 300 grain bullets (S.D. of .305) and I get 2,000 fps with my 350 grain BRTORNFPGC WQ'ed bullet (1) (S.D. of .375) in my 9.3x57 (52,000 psi on a M98 action), why would the 9.3x57, at least in that guise, not be satisfactory, using, of course, a custom 0.050" thick jacketed bullet of the same weight?

1) http://www.accuratemolds.com/bullet_detail.php?bullet=37-355H-D.png

Which is why for heavy stuff, I sold my 2 .375 H&H rifles and 2 9.3x62 chambered rifles, but still have my 3 9.3x57 chambered rifles, plus my .458, of course.