If you want your bluing to come off quick, get yourself some Orange Oil!
My custom Ruger M77 MK II in 25-05, fancy wood, pillar/action bedded and Timney trigger, has had the muzzle, an inch or so down form the muzzle on the barrel, the rear of the action, cocking piece and end of firing pin assembly completely void of any bluing cuz I was stripping other actions and barrels and put the tin of orange oil stripper in my box on my truck and the 25-06 in it's bag in as well...it leaked and ended up on those spots listed.
From a distance it almost looks like colour case hardening in those areas. Hahaha.
I will get around to re-bluing it one day, but I'm using it so often normally, could've done it during lockdown but it's kept at my parents and was outside the travel restrictions, maybe I should get it done now.
Back to the OP topic, I always soak with Hoppe's No.9 overnight and get a light green/blue indicator, so there must be some copper solvent in it. I had some Hoppe's Benchrest and that removes copper. I ran out a while back and no shops have it here.
I really like Hoppe's followed by JB Bore paste, dose a great job combo.
Cheers.