I haven't started load devlopment yet but I have some .458 sabot's for my CVA powerbolt (1/27 twist) and will try the RCBS 458-300 FN & HP and 500 gr. cast Hp's w/100 gr MOL of holy black and musket caps first. Bet that the 500s and 100 gr kick!, I'll probably start w/70 or so first though.-Muddy