Rider,
I always favored the Ideal now Lyman 457-121 PH. It was originally developed by Harry Pope and I shot it first in my 86 Winchester and on through the years. It's a little undersized for the .450-.458 bore groove but with 1/20 alloy it obturate well and for midrange accuracy it's hard to beat. It's a great hunting bullet with black powder loads that will let you shoot with out fouling control that a bore rider won't let you do.
I sent a print to Tom at accurate moulds to make a twin to the 121 that is proper for the .450/.458 bore groove and I have shot this bullet using my .45-70 and the .45-90 out to 1026 yards in Montana with some good breezes and hit the iron 8 out of 10 shots.
Here is the page at Accurate so you can see it.
http://accuratemolds.com/bullet_detail.php?bullet=46-467L
