LFOD1776 -

You've been reading stories from the history books.
With modern powders -- Accurate Arms 2230 and 2015, as well as others, getting 2150fpsMV with the 500gr bullets is not an issue at all. The Accurate Arms powders not very temperature sensitive at all, and full-kitty loads tend to transport and store without powder 'clumping' problems or hangfires or misfires.

With modern over-the-counter powders, the 458 Winchester is everything it claimed to be from the start, without the problems of the powders it was originally loaded with waay-back-when.

Cheers
Tinker