Guess there is disagreement about Rangers' barrel lengths.
I would like to offer another view on firemanjim's post - " lock which obviously is the most ESSENTIAL part of any muzzleloader"
I'd say the essential part is the barrel. It is that which goes BOOM and sends a ball somewhere. The stock & mountings are so one may point the barrel in the right direction, and the lock conveniently ignites the powder. But with a loaded barrel alone one can locate some fire and make the thing send a ball somewhere.
A very practical matter is take a good look at that Indian barrel, specifically how it is breeched. Unscrew the breech-plug and see how the threads look. They should be coarse threaded and fit well. I have seen other posts suggesting they are not all. The only one I saw was a blunderbuss some years ago with the plug quite blown out. Happily it missed the shooter's head. The musket itself may or may not suit your ideas of authenticity but one serious matter is will the plug stay in.
Authenticity? Safety is more important, to me anyway. But then I was an Expert Witness for some muzzle loader lawsuits, and have seen burst barrels and heard of the injuries to the shooter. There are always times when something goes bad. Some barrels bulge and need replaced. That's life. Other barrels don't have such ductile steel and shatter instead. That is most hurtful to the man holding it.
I shot my first muzzle loader in 1954. Have shot with local groups in four states. I never personally heard about a gun bursting. But I have done failure analyses on several that have indeed blown up. I can tell you that well-known barrel maker in West Virginia went out of the muzzle loading barrel business mid-1980's, after a union plumber blew off 3/5 of his right hand from one such barrel.
Reported in a three-part series, Oct-Nov-Dec 1985 Muzzle Blasts