I just always seemed to find some brown on my patch the next time I get a muzzleloader out. I hate to think I left some moisture or powder in there. I want it to last many years.
It's all about using the hottest soapy water you can tolerate working with. The key is to get the barrel as hot as you can handle. Run a couple dry patches through the barrel to suck out excessive moisture, then a lightly oiled patch, and then one storke with a dry patch. Set the now hot the the touch barrel aside and let the heat do it's work on any remaining moisture.
