Halger280HVMag has quoted the CGN prohibition on swapping a restricted length barrel for a non-restricted length one at a range.
The instant that a short barrel is installed, the firearm becomes a unregistered restricted firearm. Firearms lawyer Ed Burlew has defended people who tried this restricted/non-restricted barrel swapping game.
The forum is not one that I moderate, but the violation of CGN rules has been noted in the Moderator's Forum; there will be followup.
I suggest that those members who have advocated this illegal switch at a range edit their posts before the infractions start.