I shot a 120lb bear at 30yds in Maine in 2011.
Disclaimer***** The following load is my own and has been worked up by me and for me. Anyone who does not like it please don't use it. (that was for the BP purists) Lol!!
I was using a 245gr. Aeroptip Powerbelt, 5gr 3f black powder in front of 90gr. 2F Triple 7. The shot was from a tree stand with the bear at the bait barrel standing with his head and paws in the barrel. It entered just behind the right front shoulder about mid body. Proceeded in a downward angle through the heart, fragmented, with some of the bullet exiting in front of the left shoulder. The bear went about 40yds and died within 2 minutes.
My gun is a Left handed Lyman Great Plains with a modified right handed "hunter" barrel (faster twist) with peeps. This load has taken numerous deer and a 200lb russian boar (pig) with no issues. My distances have ranged from 8yds to 140yds.. If my shot is placed well ...it performs well.
Tundragriz is a guy who seems to have shot many different species with his Great plains and is a good source of info here on the site. I have seen him answer a few questions about loads and projectiles and have perused his photos a few times. I would pick his brain (as I did) and I'm sure you will come to some conclusions of your own.
Me and the bear
The shot from the tree, 30 yds.
The boar, 70yds
7pt, 22" spread, 8yds
Good luck to you and if I can help in anyway shoot me a PM or email.