Hello,

As the picture showed in my 5th post, I made a chamber cast which extends into the rifling. These barrels have 7-groove Henry-Style rifling which makes measuring across the lands difficult. Nearest can I measure is 0.506" - 0.507" groove dia.

Today I lathe turned a ball gauge to measure the bore diameter. It measured exactly 0.490" in both barrels. This would explain why the barrel flats are marked "40" and not "39". When gauging the bore a 39 gauge would not fit, but a 40 gauge would. (see chart)


How to Hunt Wisconsin Whitetail Deer with a Cannon