Need to know what powder you are using.
Regardless of how you actually clean your rifle, you should apply a lite coat of bore oil after you finish cleaning. I apply a lightly coated patch with oil followed by a dry patch to remove excess oil, then store. Then, before you shoot again, run some dry patches down the barrel to clean out the excess oil and then pop off 2-3 primers to remove any oil that might have drained back into the breech plug.
Am I to understand that you are not swabbing between each shot? Unless you are using BH 209, you should be swabbing between EACH shot. If I using pyrodex or 777, I run a "spit patch" down, both sides, followed by a dry patch, both sides, then reload for the next shot.