Last question first - - sure, minor pitting like that is not going to weaken the barrel in any significant way. I would however make sure to clean up the pitted area real well, with JB past as sabotloader suggests, or any other mildabrasive such as toothpaste or that fine cleanser made for stainless steel or aluminum.

Now, back to the original problem. In my view, this business of fouling a bore - then swabbing - then loading and leaving the load in for more than a day is just asking for trouble. Swabbing after one shot may prepare the barrel for the next shot but in no way cleans the acidic fouling out of the bore. That tiny bit of fouling left in the corners of the rifling grooves has already attracted some moisture by the time you putthe second load in. The corrosion clock is ticking. Sure, you're good for a day or two, maybe even three or four with a stainless barrel. But anything longer than that is surely working evil on the bore. Each time you do it the evil has a greater chance to grow because there are already very tiny pits there from the last time you did it.

My advice is to never leave a load in a barrel for longer than36 hours unless the barrel was squeaky clean when loaded. I have no qualms, and have never had a bit of a problemwith leaving a squeaky clean barrel loaded for months at a time. That's why I sight in so that my first shot from a clean barrel hits at the point of aim, and always hunt with a clean barrel. A second shot from the fouled barrel may be an inch or two or threeoff point of aim. That's OK. The first shot is what counts anyway.