I have this posted in the Black Powder and Reloading Forums also, so hopefully someone can offer some good advice.

I am looking for black powder cast bullet loads to use in a Browning B85 Highwall .45-70. This is the sporter version with the light octagon barrel and a 1:20 rifling twist.

Please include charge weight/grain size, and bullet style, weight, alloy, and who makes the mold or bullet.

I have a tang sight for the rifle, and intend to use it to try BPCR Silhouette. If I like the game, then I will consider a rebarrel job.

Try asking the same question at:
http://talk.shooters.com/room_14/topics.cfm
They'll know and help.
Henrik