Muley, i think his first post was buying a 50 cal which would be either a 490 or 495 ball depending on patch thickness and barrel bore, otherwise I agree with the rest of your post!
Black powder is the only way I go with Hawken style rifles especially the flintlocks. The 50's get 100gr of 3f and the 54 gets 110gr of 2f. With these loads I've never seen black unburned powder in the snow, indicating full charge burn. The Hawken book I have says the 52 cals were loaded with as much as 120 gr on a regular basis even with powder guarded like fort knox.