I use it, it’s pretty good I think. My barrels don’t foul that much but if you want to know if it’s worked remove the carbon fouling first - spray, leave 10 mins than patch clean. Then spray again and leave a few hours - if you remove carbon and copper together it’s hard to see the blue stain through the black carbon. If you remove the carbon first then on the second cleaning you can clearly see the blue copper stain. I’d love to see what a patch looks like from a heavy fouling barrel just for comparison.