I don't shoot many jacketed bullets, other than 223/5.56 and 22-250 in my rat rifles. Fortunately, none of these barrels copper-foul very badly. I got away from using Sweet's or other 30% Stronger Ammonia-based cleaners, out of concern that dozens of 15-minute dwell durations of these liquids on metals might equate to an overnight stay and resulting metal etching or damage. I use the "Wipe Out" bore foam after a hunt, then clean with Hoppe's #9 and leave the bore damp with Hoppe's and the rifle muzzle-down in the safe. I check the bores every month or so, patch out the Hoppe's and it is always at least slightly blue. I don't think any reasonable method ever gets ALL of the copper fouling out of a barrel's metal--I think it is a condition that you manage reasonably to maintain an accuracy standard, and call it "Good" from there.