I think you may be missing the point here guys?
Measure the barrel wall thickness and see if the tubes will take the necessary amount of 'reworking'.
Estimate or measure if possible, the depth of the pitting before getting yourself into deep water.
If the tubes have sufficient wall thickness, you could 'spill bore' them and then hone and polish using simple workshop tools.
Remember, Victorian gunsmiths did not have sophisticated machinery, but they had copius amounts of cheap labour time and skill.
'Make haste, slowly'.
