Cayugad - do you swab your bore with a solution prior to shooting? I know some who use a 50/50 windex/alcohol solution to wipe the bore. I heard that any petroleum product will form a tarry like residue inside the barrel when mixed with the fired/burnt black powder. I've always used bore butter and never had this problem.
Oh, BTW, as far as humidity, I mounted a ceramic light base inside my gun safe adn put a 25 watt light bulb in there. This keeps the interior of the safe warm enough to expel any humidity. Those silicon dessicant bags are nice but a pain to keep 'baking' dry. The golden rod works well too I've heard.