Has anyone tried Winchester's Supreme 500gr.Nosler partition at a claimed 2240ft/s. Velocity if true would be almost 100ft/s faster than Hornady's Superformance loading and only 60Ft/s less than that company's Lott load.
If Winchester's claim is legit it would certainly help to rehab the .458's reputation.
I own a Browning High Power Belgian Safari grade in that caliber and it is a beautifully made rifle if slightly on the light side.
I would love to try that load on Buffalo this summer.
I wont be able to answer your question, but I will make an observation that may be of interest or not.
After 20 years of shooting various 458's, a slower muzzle vel. of 2100 fps or even 2000 fps will kill buff just as well as 2200 fps and your felt recoil will be about 40% less. A lot of folks have found fault with the 458 Win. mag. because of low speeds, but when I load my own ammo, I load 500gr. bullets at just around 2100 fps because they work just as well as 2200 fps. I can produce handloads that will achieve 2200 fps out of 22 inch barrels and even had one rifle custom built for working in Alaska, that would achieve 2200 fps with its short 18.5 inch barrel and 500gr. bullets--that rifle utilized an Obermeyer barrel.
And this is an entierly different subject, but honestly, you're better served with 450gr. bullets (both softs and solids) for any African game, as the 450gr. bullets will stabilize better terminally and will normally out penetrate the 500 gr. bullets if all else is equal, as those lighter bullets stay "nose forward" better than the somewhat wobbly 500gr. bullets. Sometimes 500gr. bullets work very well and sometimes they dont, but the 450gr. bullets always do, assuming proper construction.