You can buy a Teslong USB bore scope at Amazon for around $80 that will work on your computer or your phone with no other attachments, except a USB A to C adapter for the newer phones. They make a zillion models; buy one w/o a viewer, as Windows comes with camera viewer software and Android phones have a dozen USB camera apps if one is not built in (I don't remember if I downloaded mine.) They have a variable focus and a right angle adapter.I shot 100 rounds of Lapua 6br 90 grain ammo through my Rock Creek barrel.
Then I cleaned as normal with Bore Tech Eliminator.
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Followed up with Pro Shot that did nothing better than Bore tech.
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Followed by CLR. Which did remove something that was light brown. I am assuming the stubborn carbon, but I do not have a scope.
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My conclusion is Bore Tech is still my fave and it, combined with a JB scrub probably cannot be improved much. CLR does seem to soften carbon as advertised.
You don't need to buy a viewer with it. You would be shocked at the chambering job my old gunsmith did; you can tell when your bore is clean and is not.
You can take it to the range or standing up in a backpack in its tube to the gun show.
Further, the chambers in my new M1A and 270 Savage Axis look like they were cut with a hand held drill, but when returned to the factory neither firm seemed to think there was anything wrong with them.
Don't leave home w/o it.