Salt Flat, old time gunsmiths doing sporter conversions on these rifles back in the day usually cut off the threads on the barrel shroud and slipped this down over the barrel shank to cover the threads on the front of the receiver ring. It's really the easiest way to achieve a clean sporter appearance. Oh yes, I think I know where there's a spare beat up barrel shroud off a wrecked Commission 88 rifle you might be able to purchase quite nominally if you are interested.

Good luck!