Bob- just an after thought- if I were doing this to a set of older barrels, I might consider plugging both the muzzles and breech with cork plugs, and possibly using a 4" dia length of PVC pipe with caps rather than a steel tube or iron pipe-if for no other reason than the stripper or whatever compound we figure out to be best won't "migrate" to the ID of the metal pipe- you want as close to 100% on the heavily coated tubes.