mauser: you should be o.k. with that load,I read your post the other day about the vent liner a good idea when installing the vent liner DON'T send it home just snug it.
I have a hawkens in a flinter 50 cal. 1 in 48 twist and what I use is goex 3f 100 grains and a wad and a .015 pillow think patch,lubed with a mix of 60/40 beeswax and lard @ a table spoon of olive oil and a hornady RB .the gun shoots better then I can see with this load