Glad you liked the thread. CZ550, who used to post here, did a lot of work on the .458 and published a booklet about four years ago. Perhaps you can PM him. He also has a blog:
www.bigbore.ca. Lately he's been experimenting with the 9.3x62.
Since 2008, I did some other work and concluded two things:
1. AA2230 is the best powder for heavy bullets though H335 is close.
2. I can get 2700 fps with the 350 grain TSX and no pressure signs (but using H4198. Unfortunately I cannot get this bullet to impact in the vicinity of 450 grain bullets. So it's use one or the other, depending on the game, on any particular hunt.
You should also read the nearby thread on using the .458 for plains game.
