I have never heard of anyone getting in trouble for having tape and a bottle. If you have a bottle with carbon fouling inside it and an exit hole in the end, you win the ATF's mystery prize.
FWIW I know a guy who has a "suppressor" that is little more than a serial numbered fitting that screws to his .22 that has threads for a 20oz bottle on the other end. It is registered on form 1.
Stopping power: The power some guns have to make you stop what you are doing and get your wallet out.