RE: Can't get it clean...
The only reason why I mentioned I thought it was the 209 primer is because I used to use 209's in my Encore before changing it over to .25acp ignition. When I used the 209's the breech plug and firing pin area along with the bottom of the barrel and even the scope would be covered in gunk/soot. It wasnt always to easy clean off and I have the stainless Encore. When I switched to the .25acp ignition 95% of that gunk/soot was gone. I know your muzzy probably cant be converted but I just wanted to say that its probably not the powder that is to blame. Those darn 209 shot primers are WAY over kill and it doesnt help that they are not very well sealed in the breach so lots of that fire power from it comes blowing back to cause all kinds of crud very where.