I use barns CR10 to get the copper out of my barrels and it eats it like magic. The question is about my 220Swift, I'll clean it with cr-10 until only clean patches come out, but I can still see steaks on the lands near the muzzle. More scrubbing doesn't seem to do it either. The gun still shoots half inch no problem so it doesn't bother me. I just want to know if it is really copper that is holding up to the cr-10 or does it sound like I'm smoking crack?

I've not used CR10, but if it's like Sweets, soak the barrel for 15 minutes, 20 max. Run a patch through it, if there is copper the patch will be blue, if not no copper. Be careful mixing chemicals as harsh as Sweets or CR10 and don't use a bronze brush with it cause it'll eat the brush and give a false reading.---Shoot Safe---montdoug

CR-10 is some powerful stuff and I would use it sparingly.
The copper that you see remaining is what many shooters refer to as copper wash. It is not a problem and should be left in the barrel. After all, you are still getting .5" groups with the copper wash. You can remove this copper by alternating between the CR-10 and JB bore paste. However, you will probably have to shoot a few rounds to get the barrel to settle in again and the trace copper will be right back.
You should only clean the barrel enough to return accuracy. More than that is a waste of time and may put more wear on the bore than shooting.
Just my 2 cents
VH

I agree with Varmint Hunter. You'll find copper fouling has a tendency to layer. That's why you use the JB bore compound, to expose the next layer down. If you use bronze bristled brushes, the ammonia in copper solvents will eat the bristles. You'll get bristle residue which will also be greenish-blue so you can mistake that for copper fouling as well. Use a nylon bristle brush with Barnes or Sweets, and be sure you get any copper solvent resiudue out of your barrel when finished. A good coat of Rem oil will protect the barrel nicely. Don't worry about that little copper wash. More bores have been ruined by cleaning than hunting. Best wishes.

Cal - Montreal