I am merticulous as d. Winsor with my sidelock. However, the other thing that makes BH 209 valuable to me is that it is really a smokeless powder diluted down to regular blackpowder pressures. But with my two stainless guns I use it in, I never worry about cleaning it even if I can't get to it for several weeks. So far zero rust problems but have heard of others where they thought it did rust. More humid areas or stainless barrel maybe? But it works for me. In fact, the last time I used it in Colorado in a week of hunting, occasionally misty conditions. Shot it at the middle and end of the week, and when I headed home, I just ran a couple of dry patches down it. I think I cleaned it at the end of the week after I got home. No rust. So to each his own, but that is why I like it and use it: no swabbing and very little rust problems.