As a gunsmith, most of the pitting I've seen that supposedly came from copper solvents, was in stainless barrels and from having the stuff left in for long periods (12+ hours). But some can be a problem. Chrome moly steel is less prone to it. I used to use Shooters Choice, but have switched to Montana extreme. But heed to warning someone gave about the fumes. A close sniff will knock you out! I scrub with a bronze brush & solvent. Let sit an hour, scrub with the brush again and then clean with patches and leave with Montana extreme light synthetic oil (no additives).
I still use old Hoppe's #9 as a powder solvent: not because it's any better, but because the smell reminds me of my youth
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I turkey hunted last month with a rep from the company that owns Hoppes now. Vista Outdoors He said as they'd made improvements, they worked hard to keep that smell..
