I have a Sharon Trade Rifle I built from a kit in the late 70's with a .50 cal rifle barrel. Later I picked up a .54 Sharon barrel for it. Then I wanted a 20 ga and so I bought a Green Mountain 20 gauge barrel and breeched it and fitted it myself. Making the underlug the ramrod passed through was a tricky part.
Fitting a barrel to a pre-existing stock is not easy unless it's all factory-made to fit. The tang has to precisely fit the mortise, the wedge has to precisely fit, the ramrod pipes have to line up perfectly with the ramrod groove or hole. The tang bolt, etc, has to fit the same. The drum and nipple have to be precisely the same as the other barrel. All of this is harder than doing a one-off. I would not tackle the job for less than $100 after the parts are bought.
Sharon made good solid guns, that's for sure.
