Hello. I've not been able to get a cast or plated (Rainier) bullet to really,really group for me out of a HP like a few pet jacket loads.
That said, the best I've come up with has been a cast 124 gr FP (Rucker) or Rainer's 124 gr PRN over 6.9 gr Blue Dot. This averages about 1160 ft/sec from a HP and does fairly well. It's 10 ring accurate at 15 yards on an NRA 25 yard pistol target.
Not being rude or anything, but even though this relates to BHPs, it's probably better if it's over at reloading so I'll move it there now, but leave it here (locked) so that others might contribute.
Best and good shooting.