sharps4590 has your solution. I used to experience after rusting in the bores of my flintlocks no matter how thoroughly I cleaned with soaps or detergents and scalding hot water, then dried and oiled. If I ran a patch down the bore a month or so later, it would have a reddish tinge, no matter what gun oil I used to protect it. I think I actually ruined the superb accuracy of my first flintlock from excessive cleaning more than excessive shooting.
Then I read a flier that used to come with tubes of Thompson/Center Natural Lube 1000 Bore Butter. According to them, early black powder shooters never had rusting or corrosion problems until Drake struck oil at Titusville in 1859, and petroleum based lubes replaced the animal fats and vegetable based lubes that were used previously. The instructions said to begin using the Bore Butter as patch or bullet lube after removing all traces of petroleum base oils, and to clean only with hot water. The process was said to be like seasoning a cast iron skillet, and it was important to never use bronze brushes, detergents, solvents, or agressive cleaning that would remove this seasoning. It's not something you can really see like a blackened cast iron skillet. My rifles bores are still shiny and there is no visible build-up on the lands or grooves.
I was reluctant to believe this, but I tried it and cleaned only with hot water. I then dried the bore and warmed the barrel to drive off all traces of moisture. I then protected the bores with the same Natural Lube 1000 patch and bullet lube. At first, I checked often for after rust because I couldn't believe this method could be as good as the thorough scrubbing and oiling I had done for years.
The results were astounding. Now I can clean my flintlocks with this method after deer season and put them away with a coating of Natural Lube 1000, and be confident that the bores will remain rust free until next season. Petroleum based oils or solvents and Black Powder just don't mix.
edit: if you go to Thompson/Center's website much of what I just told you along with the theory behind it can be found in the Frequently Asked Questions (FAQ)
Last edited by keith; 03/10/13 03:50 AM.