Get a Compression micrometer (not the mic. with the duck bill blades.) to see what the real thickness of your patching is. FYI......A precut patch from a plastic bag retailer ...Package labeled .015 thick , mic.s at .012 to.013. .. This thickness works for most .50 cal. bores using .490 ball. My experience is with custom rifle barrels ,Colerain , Rice , Getz , etc.. Not familiar w/ modern factory m/l ing bores.
I use one of the grease lubes. The trick is to , remove as much grease from each patch as possible . I lube with minimal grease , by greasing my patches , before going shooting , thus eliminating one chore at the range. Another thing , FFFg black powder , burns a little cleaner than FFg. To eliminate powder ash rings in your bore , wipe as often as needed. Commercial bore cleaners work , but so do the home brew bore cleaners . Keep the bore free of ash , and you will do well. .......oldwood