I used H4895 with loads to 2,200fps using cast bullets of 505gr. in my .458 Alaskan - virtualy identical case capacity to the .458Win Mag.

From 1,800fps (where I started) on up, it held MOA at 100 meters using the Lee 500gr. GC bullet from straight Wheel Weights with Lyman moly lube - no leading at all.