As Scott indicated the Knight 52 with the 1/26 twist certainly showed it could shoot the long .458 bullets with great accuracy. And I believe Grouse has shown how well it works with the short stubby .458x220 Bloodline.
I never shot those big Knight 375s for the 52cal. Cost and recoil are just too much. The 325gr FTX with 130gr of BH209 was enough of that. A ASG 310gr bullet made by Rocky Mountain for SmokelessMZ (similar to the Parker MH) probably flies just as flat or better than the big Knight .475 375gr.
I would still love to see something around 240gr in a 40cal cup and core for sabots. A 240gr should fit existing sabots. The PR bullets fit them and they make upto a 260gr. A 40cal 230gr or 240gr should also still shoot in a 1-28.
A BC of .275 should be a cake walk considering a 200gr SST is around .250.