The risk hunting grizzly bears isn't about the bear getting you it's about the bear getting away! Why wound a grizzly bear with a muzzleloader so that the guide has to kill it for you. Something to think about.
If the shot is placed properly the ML is just as deadly as any modern rifle. So long as the ball is properly sized for the game. Part of the problem, like Turner Kirkland’s Elephant hunt with a 4 bore, is in using soft lead balls on large game. While we read of John Taylor killing a number of African Elephant and Rhino with a 10 bore and hardened balls. Kirkland shot an Elephant twice with soft lead from the 4 bore and the PH had to finish it off due to insufficient penetration. Poor bullet/cartridge selection is a problem with brass suppository guns as well and bad shot placement certainly is.
The average American hunter going to the Western Mountains in 1835 would likely take a 54. Its not all that great but it works for almost everything so long as shot placement is good. And moist American in the East saw little reason to shoot. A ball size larger than 38-40 to the pound. Larger boires were to expensice to shoot. But like Taylor stated, facing a charge with something a little too small, and a 10 bore was pretty small for a ML in Africa, with only one shot, was not something he would have wanted to do.
Shot placement. With a proper caliber I would not worry about a shoulder shot on a bear. According to reports it works and a medium high shoulder shot will anchor just about anything you would find in NA if penetration is adequate. I can’t go on without getting too far into brass suppository territory. But remember that Lewis and Clark were shooting pretty light loads in the short rifles, based on Lewis being shot with one. So the effectiveness on Gbears may have been poor penetration if the penetration in Lewis’ butt was any indication.
I am supposed to be doing something in the shop now….
