Dan posted "I do not believe that a polished bore will enhance copper streaking-it's total BS.".
I shoot benchrest..custom guns..and a polished barrel do not or almost do not retain any copper.
I shoot a .30BR -115 grains at 3150 fps. NO copper in the bore. My Bartlein barrel is cleaned every 20 rounds..shiny like chrome..
This is facts..polished barrel copper out way less or not at all.
And yes..I use a borescope to make sure it’s squeaky clean.
I use this below + JB as needed on all my guns.

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