Well as I said I have a .54 caliber barrel I have been cleaning the water/soap/bore butter way as a test barrel you might say... So far some suspicious results with the brown liquid (I really do not think it was rust) that swabbed out prior to shooting. Accuracy still holding in there. Loading about the same as the other rifles. Fowling about the same too.
Yesterday I shot my Flintlock Hawkins which I clean by a much more modern method of a soap and water bath followed by solvent patches, solvent brushing, more solvent patches, isopropyl patches, then dry patches before the final gun oil patches. Accuracy about the same (excellent! :: ), Loading shot to shot still easy, fowling about the same also.
I am starting to think that what ever method you feel comfortable with and have faith in, is the method to use. Both seem to be working although I have my doubts about down the road accuracy with the bore butter. I went through this once before..