Many fine British shotguns were ORIGINALY made with thin barrels, especially if they were light weight. The ounces have to come from somewhere, after all. Also many American classic doubles were originally made with thin barrels, the makers simply didn't measure them while striking. Generally 22 thou is not out of the ordinary for best barrels on a light gun that have not been honed, polished, or cleaned down on the exterior after dent removal. Check for bore diameter and compare with proof marks as well as factory weight if available.
Best,
Mal
