No I don' agree with remington!!! I am sure I get all the copper out of my bores I have used sweets and CR10 mainly to remove copper. I can tell you my bores are sticky clean and not one speck of blue shows when finished with them. It sound to me like everyone you talk to is shifting blame and really not offering any solutions just covering there own tails. If copper is the problem then try using some CR10 it has worked well for me when tackling some dirty bores in the past.

Make sure your scope and mounts are AOK.
Try different ammo, gr, etc.

If all else fails then talk to a different gunsmith about the bedding or other issues.

Good Luck