I haven't had it done but I have an old Remington Wingmaster barrel with a fixed full choke which I would like to get the barrel threaded to accept screw in chokes.
Here's the link to have it done. Carlson's Shotgun Choke Tubes and accessories for the hunter and shooter
Here's the link to have it done. Carlson's Shotgun Choke Tubes and accessories for the hunter and shooter