Mooshoo,
As I mentioned on another post, I thought 350 grain bullets were ideal for North American game in the West. I loaded 350 grain TSXs using F215 primers and H4198 powder. With 80 grains I could easily get 2700 fps in the 22" barrel of my Model 70. By "easily" I mean the empty cases just about fell out of the rifle. I eventually settled on 75 grains, though, a low pressure load in my opinion. Velocity was 2600. 78 grains yielded 2670. 5-shot groups with both of these loads were 2.25" at 100 yards.
The .458 is one helluva cartridge. If Winchester had any intelligent marketing people, they would have brought out a load similar to the above. I also played with 450 and 500 grain bullets for African dangerous game. I never used 400 grain bullets.
I would also second the poster who recommended Sir Bob's blog. He comes out with something new about every month or so.
"5-shot groups with these loads were 2.25" at 100 yards"
You could have gotten those groups a couple of times but to say what you said above and imply that this is what the rifle would shoot many or most of the time is misleading to say the least.What about the times when those groups were 6,7 or 8 inches large? Those don't count eh?
