I have an original, Damascus barreled J.P. Clabrough and Sons shotgun chambered for 2 & 1/2" 12 Ga shells. The shotgun is in excellent condition, smooth shiny bores, tight, and still with some case color on the receiver. Gunsmith has inspected the gun and pronounced it in excellent condition and safe to shoot. Measurements of the wall thickness indicate that the barrels are original and have not been honed. I would like to use smokeless powder in this shotgun. I am very experienced in developing smokeless loads for original black powder rifles, but have no experience at all with shotgun cartridges.
I would like one or two smokeless loads that generate peak pressures no higher than black powder but deliver the pellets at original black powder velocities. I have read Sherman Bell's tests of old beater shotguns, including Damascus barreled shotguns, so would prefer not to get deluged with warnings about shooting a Damascus barreled shotgun. I would be very grateful for some direction on some smokeless loads. I have 2 & 1/2" casings, I just need some direction and have not been able to find anything from my usual sources.
