From one of my correspondents on : BULLETS for Big Bores - the .458 Winchester Magnum
"One crazy combination that works in the .458 Win Mag Ruger is a Lehigh 528 grain Match Solid over 74 grains of H335 at an overall length of, get this, 4.22 inches. My tests with that one gave 2186 fps at a measured pressure of 60 kpsi."
Lately, I've been getting some gems from the .458 WIN fraternity.