The paradox bbl isn't a new idea to be sure I've an older shotgun that as it stands is neither valuable nor terribly useful. Its and old JC Higgins w/the "beer can"compensator screw in chokes modified only. W/o the "beer can" its just a cylinder bore w/a rib and no bead. After much reading it seems a tight imp/cyl is about optimum for heavy buck . It only takes a little spin like 1-48-60 for a round ball.
So if I make a mandrill ,generally, .720 tapered to .710 w/4"flats"at .700 ,arbitrarily ,over 4" w/something resembling a 1-48 twist. Could it be placed in the bore and the bbl be shock cooled w/dry ice to form the bbl around the mandrill or should I resort to some more conventional means?