I always cleaned mine with scalding hot water, then oiled 'em up big time. Haven't shot any black powder for years but I have noticed they now have black powder specific solvent.
Make sure you have planty of grease on hand to fill each chamber once it is loaded. If you fail to grease the chambers you can have a disatrous chain fire. I had one, was very lucky in that I didn't get hurt but the gun was toast afterwards, all because I got lazy (or in a hurry...can't recall) and didn't grease up. Three chambers went when I touched of the first one
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Mike Tangas
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72
'02 CLK320 Cabriolet - wifey's mid-life crisis
2012 VW Jetta Sportwagon TDI...at least its a diesel
Non illegitemae carborundum.