How do you know it's a "ball & powder" muzzleloader ?
If it's not an original muzzleloader, the rifling's twist might be stamped into the outside of the barrel somewhere.
If it is, 1-28" indicates a barrel suitable for conicals/sabots; 1:66" for a patched round lead ball; and 1"48" a compromise twist suitable for either.
For $100, while the outside may look perfect, the bore could be as rusty as a sewer - the very first thing that should be done is to ensure it's not loaded, via dropping the ramrod downbore, marking it at the muzzle, then withdrawing the rod & hole it alongside the barrel with your mark again next to the muzzle.
If the end of the rod ends up near the nipple (if it's a caplock) or flash hole (if a flintlock), it's unloaded, but if the end is more then an inch or two forward, there's a good chance someone left a load in there.
If the gun's name/brand is actually "Whitetail", then it's a fairly decent buy @ $100 - as long as the bore's not rusted.
If it's a Traditions Whitetail, this one just sold for a bit less.
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