Remington at one time made rifled tubes for their double shotguns. I have one in .40 50 Sharps bottle neck caliber. It is an all steel full length tube threaded at the muzzle for a nut with a taper on the rear end to center the tube in the bore.The insert has a sliding extractor like the ones found on Briley small bore shotgun inserts.
I forgot to mention. That 750 buys iron sights, means of attaching scope and ability to regulate barrel poi. I'm guessing for less than set of them antiqued Remington barrel inserts?
