[skeet]

Zazu...the bore of the bbl can't be two different sizes. Now if you are measuring the end of the choke where the shot enters and exits I understand the measurements. You will have to have a bore gauge to measure the size of the bore.. The reason that the part of the choke that the shot enters is larger is so that the choke won't be blown out of the bbl when the shot hits. They are making that larger so they can cover their butt on fitting any gun. It really has nothing to do with how it chokes the shot. Also most chokes have the choked area inside the choke a little way. Briley does it with a parallel section in the choke....in the extended chokes usually about an inch in length. And again...chokes don't always work the way they are designed to do. Every shotgun and choke is a law unto itself. That steel undertaker choke. Was it designed for the larger steel or what? They are usually designated on the package.