Graem Wright's book on shooting British double rifles has a chapter on Paradoxes. I have corresponded with him on the guns as I want to make one using screw chokes. Nice fellow, generous with his time and information. He referred me a friend of his that did exactly that using Briley rifled choke tubes. He was getting 4-6" compound groups at 100m. The friend said that the rifled tubes patterned shot almost as well as smooth tubes.