Thanks, Huvius. Good suggestions and observations. These barrels were slugged. Cerrosafe is sitting here waiting to be used, just have not gotten to it yet. Two inches below the chamber the bore is .465 average between the high and low measurements. The muzzles average (Rule of Halves) .461. The leade is fascinating, because there is no real distinct chamber. Rather, the barrel ovals just kind of blend and fade up into the chamber area. Fired case mouths are not perfectly round. The chamber area is very generously sized. Rounds kind of dangle in there. Not a tight fit by any definition.
I have yet to find a Lancaster oval bore discussion on line that is satisfactory for anyone, especially the original poster. These are tough guns to master, unless you already have the cased tools or the original shells. Few were made. Lancaster calls for these bullets to get two wraps of paper. Bullet sits over millboard and greased cloth, then 100 grains of Curtiss & Harvey's #6. Perhaps this gun did use a smooth bullet. I would use it in a heartbeat, if I knew what it was. But I am afraid of damaging the gun, so grooved bullets are what I use, so they can really move around and absorb all the swaging that goes on through the bore. I am open to all ideas.