If you are using TC 13 Bore Cleaner, there are better choices. The stuff does not have a good reputation. Good old warm water and a bit of dish soap does a better job in my opinion. Remove the barrel from the stock, remove the nipple, put some warm water in a container, and pump with a tight patch and jag combination. Don’t forget to use muzzle protector if you have one. Repeat with just warm water, they dry with compressed air if available, followed with WD40. Store the barrel over night muzzle down. Take another look the next day and see what the bore looks like. May need to follow up with a bore brush and a solvent to remove lead if that what you find. Could try one of those foaming cleaners like Wipe-Out and or a bore polish such as J-Bs. That will likely get your bore as clean as you can get it without lapping, at least in my opinion. Once clean, try some patched roundballs. Most every TC 1-48 barrel will shoot them well.