I have a movie rifle.
A bunch of them were sold by Little Johns Auction several years ago when the movie prop company that owed then closed down.
Mine was used in the old Audie Murphy movie 'Sergeant York', in the shooting match back ground scenes.
It's an original rifle, most likely a Nicolas Hawk, although the PB finale and door were lost somewhere along the line and replaced with a triangular piece of brass.
I posted pictures of it on here a couple years ago.
Most of the guns sold by Little Johns were altered Trapdoors as Dan mentioned, although some were original Kentucky's, some by very well known makers.
The really Big Bucks guns were the Colts and Winchesters used by Big Stars like John Wayne, etc. , and brought many tens of thousands!
John