Waldo-

There is a good article in the book Big Bore Rifles and Cartridges from Wolffe Publishing, by Bob Hagel. Page 328 start.
On page 329 he lists loads that are approx. equal to .458 Win.

85 grains of IMR 4064 under the 500 grain Hornady gave 2102 FPS from his 26" Wtby rifle.

80 grains of IMR 3031 under the 500 grain Hornady gave
2066 FPS.

85 grains of IMR 4064 under the 350 Hornady gave 2183 FPS with poor accuracy.

80 grains of IMR 3031 under the 350 Hornady gave 2120 FPS with good accuracy.



No loads listed in the chart for cast bullets.