Looks a bit neglected sadly. I think it's a fowling piece (shotgun) from the style and the lightweight appearance of the stock. It could be a rifle though it's hard to see if it has a rear sight and the muzzle is rusted to the point where I can't say if it has rifling or not. It looks like it has an Enfield pattern lock with Crown markings on it. At first glance I thought it could be a cut down musket but looking at the stock I think not. More likely someone simply re-used some military parts to build a new gun. Also looks like a center punch was used to spell out something on the barrel, perhaps an owners name?
