I don't know is it? Meaning have you noticed a decline in accuracy?

Personally I would use a dedicated copper remover in any regards, b/c as mentioned leaving it can cause problems down the road. First off I would use a normal solvent (like shooters choice, hoppe's, etc) this will remove the powder,lead, etcrisdue. Then run a CR solvent such as CR10 or Sweets 7.62. Once you have completed the CR stage (meaning your not pulling patchs with blue on them any longer), run a saturated patch with light gun oil or isopropyl alcoholon it to remove any remain CR solvent (if left in the bore for extended periods it can also attack the steel) andfollow that with a dry patch. Finally run a patch with light gun oil to protect the bore. Before shooting it, run a dry patch to ensure no excess oil remains in the bore. A trick to remind yourself is tie a rag on the rifle.