An acquaintance advises very good results with a product from Mercury for marine engines - to dissolve / remove carbon build-up. I have never used it, but I have used "Clean-R-Carb" from Canadian Tire (?) or maybe NAPA (?) a few times - seems to dissolve the crud nicely. I have not used that in regular using guns - mostly is literally "rusty / crusty" elderly former mil-surps that likely have never had any cleaning or maintenance in past 50 or more years.
Like OP mentions - I also use a lot of foaming Wipe-Out - I put the rifle horizontal in a vise or gun cradle, give the bore a shot and let it do it's thing overnight or all day - so like 10 hours or more, in there. For very dirty and/or elderly bores, is not uncommon to scrub with a newish bore brush before the first patch - as if the mechanical scrubbing loosens up some of the stuff that has been softened by the WipeOut soak. In some cases, might have to repeat that cycle 4 or 5 times before getting a clean, but wet, patch to come out.
And like the OP, I often take a look in there with a bore scope - always amazes me that what I think is a decent enough "shooter" and "hunting" rifle has so much pitting / cavities within the grooves and on the side of the rifling. I still do not know how to predict by looking at the bore, which one will or will not shoot "good enough". I also have looked into unfired Schultz and Larson, and an unfired McGowen barrel, so I think that I know what a good barrel should look like in a bore scope.
