What's not removed by Hoppe's n°9 & a nylon brush, stays on. It won't be much more than discoloration & will not impede proper functioning.
On stainless it CAN be removed with a "lead wipe-away"cloth (removes bluing !) or Remington's bore cleaner & a fair deal of elbow grease, though.
On stainless it CAN be removed with a "lead wipe-away"cloth (removes bluing !) or Remington's bore cleaner & a fair deal of elbow grease, though.