I may pick up an ol' crotch English hammer gun of 12 gauge with "dark and pitted" damascus barrels. Shows overall long and hard use for a circa 1900 gun. I would like to do a mechanical restoration of the barrels and perhaps reduce to a "backbored and opened" 16 gauge. That would be a worst case circumstance if barrels clean up thin and weak. Thus the original barrel would be a carrier for the sleeve which might be a 16 ga. The chambers, expected to be bad, would also be sleeved to the proper gauge. Barrels are 30". Chambers are likely 2.5". The object is to fire a 2.5" 12 or 16.
Let's assume we trim the bore true and determine diameter. This can be done via solvent application, hand brushing followed by some light emery work, and more washing with penetrants. This should have loosened globners of oxidation without tearing them out by the roots and thus making deeper pits.
My inclination is to go down the bore with a slotted dowel fitted with a steel rule strip of whatever thickness but with a taper on the leading edge. This would provide a fairly straight edge which should scrape the bore reasonably true of embedded oxidation. A technique similar to this with a tapered dowl is/was used to make bagpipe chanters and oboes. With the bore cleaned out it could be progressively honed clean.
Now: What sort of sleeving material can be used? I have shotgun barrel blanks made from chrome moly tubing. Should we take a proper grade of similar material, cut to length and grind the interior or exterior as required, and then slide this in? What is a preferred fastening method which would not promote corrosion of the imperfect damascus mating bore surface? In that regard it might even be practical to use Brownell's Oxy hand applied "blue" as it seems to be a chemical neutralizer that dissolves rust. The other consideration is the insertion of the sleeve and what the tolerances and techniques are for that operation.
Let's assume we trim the bore true and determine diameter. This can be done via solvent application, hand brushing followed by some light emery work, and more washing with penetrants. This should have loosened globners of oxidation without tearing them out by the roots and thus making deeper pits.
My inclination is to go down the bore with a slotted dowel fitted with a steel rule strip of whatever thickness but with a taper on the leading edge. This would provide a fairly straight edge which should scrape the bore reasonably true of embedded oxidation. A technique similar to this with a tapered dowl is/was used to make bagpipe chanters and oboes. With the bore cleaned out it could be progressively honed clean.
Now: What sort of sleeving material can be used? I have shotgun barrel blanks made from chrome moly tubing. Should we take a proper grade of similar material, cut to length and grind the interior or exterior as required, and then slide this in? What is a preferred fastening method which would not promote corrosion of the imperfect damascus mating bore surface? In that regard it might even be practical to use Brownell's Oxy hand applied "blue" as it seems to be a chemical neutralizer that dissolves rust. The other consideration is the insertion of the sleeve and what the tolerances and techniques are for that operation.