Members here are using modern petroleum based Cleaner Lubricant Protector oils. There are also many on the Forum that only use animal or vegetable-based oils for lubricants and rust protection and water for cleaning. What I have seen is too much oil, whether animal based, vegetable-based or petroleum based, will develop that nasty black tar and difficult to remove crust rings. Keeping the patch damp will help, but not eliminate, a crust ring. Using a damp patch with a procedure to keep the flash channel clean will take care of the black tar development. Most of the black tar is powder fouling and humidity drawn from the air or very wet patches. We do have to be aware of what is happening in our barrels. As @SmokepoleSam observes, we have to keep the oils and cleaning stuff under control. This means removing the oils before going to the range. This means storing the gun with the muzzle down to allow the oils to drain away from the breech. This means clearing the flash channel to prevent the buildup of fouling. The most important thing to remember is that if your procedure works for you, then what you are doing is correct even if it is different from what others are doing.
The "black tar" gue/crust only happens when modern oils are present when the gun is shot.
