As to the original topic, I have no doubt that a cool hand with a good roundball gun can take even the big stuff cleanly. This means he must be willing to pass shots which may not reasonably be expected to result in an animal on the ground, pretty close to where it was hit. But that applies to hunting with any firearm, be it a heavy revolver or whatever.
The 'conventional wisdom' on BP rifle types, twist rates and projectile types is usually pretty sound but there are exceptions. We have an old Traditions Hawken that is 1:66 and really shouldn't shoot well with conicals. Evidently the rifle doesn't know this because with 90-100 grains of Pyrodex, it will hold 3 inches at 100 yards using a 385 grain Great Plains bullet.
I also have an Italian Santa Fe Hawken in .54, which has produced some 200 yard groups just over 6 inches, using Triple Seven, a Hornady ball and 'just the right patch'.
I realize that 3 MOA at either distance is no great shakes in the accuracy department, but I'm not complaining either considering 50+ year old eyes and traditional sights. I am certain that either gun will produce sure killing field shots at 100 yards, if conditions allow it. I have practiced a fast reload with the .54 using a naked (.530) ball, which is a snug fit in this gun. At 50 yards it still shoots to the sights and explodes a water jug with the same authority as patched ball.
Dangerous game, alone, BP weapons only? I just might try it, adding a pair of .54 plains pistols loaded heavy, a big knife, and an axe.
PS- nearly forgot...no I do not favor 'limits' or regulations on the subject matter.