so he hada screw in choke? if it was 3.5 it had to be, mark never built a screw in choke, though his name was on some that he made to spec's designed by someone I think they were called jellyhead? but not sure, mark put sleeves in shotguns back before there was a screw in choke, ya wanna see what they will do,come down one day,bring your 10 ga, we will compare, have never saw anything that can compete with marks turkey/predator sleeve, he measured every one at the forcing cone and built a sleeve for it depending on the size using x amount of constriction, my bansner shotgun was eliminated from every shooting match held within 50 miles because no others could come close to delivering the same patterns.Mark now builds a little better than average rifles
RR