I started using this stuff for all sorts of applications recently: https://clenzoil.com/collections/field-range
It cleans things extremely well, and leaves a nice corrosion resistant coating that doesn't get sticky or gummy or evaporate away either. And it treats and conditions leather and wood quite well too. I haven't tested it to see how well it removes copper fouling, but they claim it does. For general gun cleaning and protection I love it though. Makes it so fast to be able to do in one step, especially if you saturate a bore snake with it. I haven't been a big fan of bore snakes in the past, but with clenzoil I find myself using them more now.
It has quite the history behind it, been around since the 1940's. The company was bought in the mid-2000's and was pretty much impossible to find for a while, until it was sold again this time to a more business savvy vet, and is finally easy to purchase and getting easier by the day.
I was first introduced to it when a muzzleloader I bought around 2001 came with some pre-saturated patches. Never bothered to use them much until a few years ago, and found myself really liking the stuff. Then was disappointed to find out I couldn't find it anywhere. That is until recently. With the new owners and now easily available, I bought a couple bottles in liquid form. They'll even send you free samples to try. Just in the last couple weeks I've cleaned and oiled guns, cleaned and treated a pair of shoes, and cleaned up a couple trailer hitch ball mounts with it.
2004 TRX400FA (Rancher 400AT)
MotionPro twist throttle kit
12" handlebar mounted light bar
rear rack wheelchair carrier
Cycle Country 48" plow w/ KFI hybrid mount
Champion 3000 lb winch w/ synthetic rope
23" Titan 489's all around (saving clutch)
2011 Grizzly 450 EPS
Others in the family: '04 TRX250TE, '85 TRX250 Utility (X2), '05 TRX90, '06 TRX500FA, '95 TRX400FW,' 88 TRX125