The light charges might work just fine in that fast twist with round balls. I'd be more inclined to make a mould for a flat nosed, 'picket' bullet of about 350gr. weight for the rifle - patched in lubricated linen or denim, and not load to the 'chamer's' size. IE: I'd load it with 75 to 90gr. 2F and turn it into a real hunting rifle. I'd also prefer these charges for any big game.

I know a pistol will handle game with round ball, especially in a .50 to .54 cal. using 40 to 60gr. of powder. I just prefer a bit more. A 200gr. bullet or ball doing 1,473fps will produce about the same power as a .44 mag. does, so there really isn't any reason not to use it at under 100 yards on deer, etc. A .54 ball will completely penetrate a moose, side to side if making 1,000fps. That I now for a fact - I just prefer more.