What I've heard is its a rifled barrel that takes a screw in choke. When shooting .45 the choke should be removed allowing the rifling to work. When shooting 410 the choke acts as a choke as well as straight rifling. The straight rifling is to stop the rotation of the shotcup so the 410 will act as a normal shotgun. The choke is rifled but with no rotation at all to negate the rifling of the barrel. Otherwise the rifled barrel would spray the shot all over the place.