I’ve seen this image somewhere. I don’t remember where. I’m not sure the subject is African-American, but just heavily tanned. I’m serious.
If you expand the image, you see the musket uses an early conversion technique, with the nipple screwed into the top of the barrel, a little right of center. The hammer is bent to reach the nipple. Also, the breech end of the barrel appears octagonal to me. So I would respectfully suggest it is not an 1842, or even an American gun at all. Maybe Belgian or Prussian.
The powder horn looks as if it has a band around the base. It has a very unusual appearance.
I’m going with an authentic antique photo of a poor hunter in Northern Europe, late 19th or early 20th century. He is shooting a muzzle loader for the same reason poor people in the backwoods were using them here during the same time period.
I could be wrong. It's been known to happen. Just ask my wife…
Notchy Bob