In 2006 I built the rifle you reference in the above photo. It had a 58 cal. O/R barrel 34" long. The barrel was cut down from a standard Colerain 38" O/R rifled 58 cal. barrel. The stock was figured cherry, stained with lye. All the silver inlays were sterling silver as was the sideplate. The gun was built for a client going on a moose hunt. Unfortinately, due to health reasons he never got to take the trip. I have no references to support using the O/R barrel, but it worked out rather nicely for this project. The finished rifle weighed in at 7 lbs, a nice light hunting rifle with some punch.
Best wishes
Ron