9 mm Revolver Bores
A big fan of the Smith & Wesson Centennial revolvers-he carries one every day-Wiley Clapp thinks there needs to be a J-frame chambered in 9 mm Luger.
Terminology: Bore Diameter/Groove Diameter
Here's the definition, right out of the NRA Firearms Sourcebook. It is “...the minor interior diameter of a barrel that is the diameter of a circle formed by the tops of the lands.”