I use Sweet's 7.62 to take care of the copper fouling in my only rifle that has that problem. The stuff is amazing. Be careful with it, though, and follow the instructions to the letter. It will actually etch the barrel if you are careless with it.
Here's the offending rifle. It's a Ruger #1 with a 28" long 1:12" twist Lilja barrel chambered in .220 Swift, with a Leupold Vari-X III 6.5-20X scope. Handloads with the 60 grain Hornady Ballistic tip and either IMR 4350 or Reloder 22 just touch 3,800 fps.
