I don't think you need a gunsmith to solve your problem. From the photo I don't see any rust inside the bore, maybe you have a bit of jacket fouling which can be removed with a product like Wipeout foaming bore cleaner. I typically fill the bore with this stuff, allow it to work overnight, and patch it out in the morning. Some extra-fine steel wool soaked in oil used lightly over the problem areas of the external surfaces won't cut through the bluing. If you do have rust in the bore, an application of J-B bore paste and Kroil will clean up the bore. Soak the bore with Kroil, or a similar penetrating oil. allow it to sit for a few hours, then apply the bore past to a tight fitting patch or a bore brush and gently work it back and forth, advancing an inch at a time, though the full length of the bore. Occasionally patch out the bore by running 2 or 3 patches soaked in solvent through the bore to remove the bore paste, then patch the bore dry and examine the progress. Repeat as required.
