It is a smoothbore fowling piece converted from flint to percussion. It is not a rifle, it is the equivalent of a shotgun. The contour of the lock plate makes me think late Revolutionary to War of 1812 era. The stock looks to be walnut, but could be cherry. Take a look over at American Longrifle dot com. Loads of good stuff there. If you post the photos you will get more info from a group more focused in that area. It is a very nice piece from what I can see. How did you come to have it?
"A Liberal is someone who doesn't care what you do, as long as it's mandatory". - Charles Krauthammer