SDH;
I have never actually jugged a bbl by any means. I did spend 35+ years working in macne shops so familar wth most aspects of metal working. For ceretain with a boring bar in a lathe it would matter not if the bore were open or not. Easiest of course would be on an individual bbl, then the breech could be simply chucked & muzzle run in a steady rest. To do it on a double I would build a fixture to put the muzzles in, chuck the breeches with bore of the bbl to choke on a center & turn the fixture true to run in steady rest. Either way it would, once set-up, be quite simple to bore the jug.
I don't know per-sey that reamer was actually the proper term, but used it for want of a better one. I saw a drawing on this in a feature the Rifleman used to run, back in the good old days. It used a flat tool steel blade let down for a tight fit into a wood dowel. The center of the dowel was drilled for a pin having a taper section at the end. To start the blade had to be down so it would enter the bore of course, then it was wedged up tight from one end to start the cutting. By continual adjusting & cutting according to the author a nice jug choke could be worked in. It might be more correct to call this a hand operted boring bar. The tool should be jacked up on the end away from the muzzle so the jug will end with a cone toward muzzle.
This was given as a way to choke ML'ers without the necessity of pulling the breech plugs. While it may not be the ideal it is a possibility. If I have learned nothing else in what will,in about another 6 weeks be 74 years, it is that if one uses the terms "Never" or "Always" it will "Nearly Always" come back & bite you.
