Sir Bob, You will not be disappointed. Inside of 200 yards it will be a deer wonder, not mere wounder of deer. Bubba's youtube prononcement on that bullet from a Hornady .45-70 factory load at about 2000 fps MV was that it is superior to a .300 WinMag inside of 200 yards. That was based on his skin-on-bone-in pork shoulder demolition and water jug penetration tests.
That MonoFlex ought to be a standard factory load by Hornady for the .458 WinMag, same as you have loaded it. It might be soon, what with the way the .458 Winchester Magnum Brotherhood is growing by leaps and bounds.
Ron aka "Rip" for Riflecrank Internationale Permanente NRA Life Benefactor and Beneficiary .458 Winchester Magnum, Magnanimous in Victory THE WALKING DEAD does so remind me of Democrap voters. Donkeypox.