I was using real black powder the other day for the first time. Up until then I have been using substitutes. Apparently my cleaning routine was inadequate for black powder. I encountered flash rust for the first time. I was able to get the barrel under control as well as the area under the nipple. No doubt it is in the fire channel. My question is how do I address it? Some of you might recall an earlier post about the clean-out screw being rusted in place. I was never able to get the screw out so that's not an option. It's too bad it is or I would have just run a 22 caliber Barrel brush down the channel. The only thing I've been able to get into this tiny space has been a pipe cleaner and even then not very well. Thank you for your help.