I've also had some recent doubts about Butch's, what I've been using now for about 6 years.
Recently it does seem to be less effective on copper removal.
Breaking in a new Krieger barrel, as I speak, & when cleaning on the range, patch's were coming out white after the easy to remove powder fouling was removed. Thought to myself, " This barrel is not copper fouling at all".
Then when I got home, after a total of 20 shots had been fired, since new, borescoped the barrel & saw heavy copper fouling in the grooves, beginning at the throat & continueing for about 5 or 6", then no copper to the muzzle. Soaked the barrel overnight, with the muzzle down and in a white plastic pill bottle. Next morning solvent in the bottle was almost the color of the original Butch's. Dried out the bore, scoped with my Hawkeye & all the copper remained.
Then gave it the JB/ bronze brush treatment & copper is gone completely.
I'm wondering if, as happened to "Shooters Choice", the EPA made Butch's change the formula, making it less effective? Just a thought. May have to consider some other solvent.