I've been using KG solvents ever since reading some articles summarizing their cleaning efficiency.
Here's a link to one that provides a table listing the amount of copper removed under controlled test conditions:
https://www.coretacsolutions.com/products_KG_KG12_TEST.htm
Here's another testimonial:
https://www.thetruthaboutguns.com/gear-review-kg-industries-solvents/
Amazing products. I do keep some JB Bore Paste and Kroil on hand but use that sparingly. Always concerned about getting too aggressive with a lapping compound!!
Statement from their webpage:
KG-12 was originally developed to clean the copper fouling from large bore military weapons. KG-12 provides professional shooters, gunsmiths, armorers, hunters and other firearm enthusiasts with a product that will remove the toughest copper fouling without damaging the bore. Unlike ammonia-based products, there is no need to neutralize KG-12 or to remove it quickly because KG-12 contains no ammonia. There is no better copper remover out there!
All the other products are too much work, stink and mess.