I have read a few tests of the different bore solvents. The products that come out on top for copper removal are:
KG12 (not made with ammonia)
Wipe Out with Accelerator
I have been using KG12 for copper and KG1 for carbon. My bores clean up fairly easily now.
Just remember, if you are making the bores squeaky clean, they may need some fouling shots to get back to the sweet spot.