What do you see when you check out the following.
I see either a line thrower, or possible a grenade launcher, primarily because the gun has no sights.
A couple of notes on it, 17 inch barrel, with 3.25 inch at the muzzle turned down to about .75 inch. There is a grove cut in the top of the receiver & only barrel band. The rifling was drilled out, leading more to the premises that a blank charge was propelling something slide over the end of the barrel.
I built a replica Ketchum, core a 1/2" line float. If barrel was in better shape, I would actually try it.
Brian