Copper fouling needs to be removed by chemical means rather than mechanical means. When the bullet is still travelling down your rifle barrel, the burning powder is actually a plasma rather than just a hot gas. Copper is soluble in this plasma, and as the bullet exits the barrel the plasma reverts to a hot gas, whereby the copper "plates out" on the inside of the barrel. You need a product like Shooter's Choice, Sweet's 7.62, or my personal favorite, the lowly Birchwood Casey Bore Scrubber. Birchwood Casey advertises that its bore scrubber removes both copper and nitro fouling, and in my experience it actually performs as advertised. It has removed copper from some ex-military rifles of mine after patches of Shooter's Choice came out clean, and it seems to be less aggressive toards the steel. You've got to be really careful with copper removers cuz they can and will mess your bore up if you leave them in too long.

Never used a bore snake, but friends who have swear by them.

For copper fouling I found Kroil to work pretty good