*The discussion of the creation, fabrication, or modification of airgun moderators is prohibited. The discussion of any "adapters" used to convert an airgun moderator to a firearm silencer will result in immediate termination of the account.*
As I understand it, it is a hosing tester. Rawroots pre-hose-clamps the barrel to see if there would be any hosing if a costly barrel band were purchased and added. If the the hosing tester comes up negative, then Rawroots would have gotten hosed buying the expensive band.
Would that be a scrap of Paprgauge we see between barrel and air tube, at the hosing tester? Paprgauge is like Plastigauge but made of thick paper or thin cardboard and measures stress instead of thickness. You take a piece of Paprgauge, write "80" in crayon, fold just after the zero and insert in the area to be stressed. Remove and unfold, and if it reads "BOOB" then there was a lot of stress but the tension has been relieved.