My cabinet also looks like the evolution of bore solvents....I never give up...never.
I clean my neighbors Savage's and Military rifles...really a challenge.
I had Shooter's choice, Butches, CR-10, Kg-12, Sweet's, and Montana Extreme Copper Killer.
Montana Extreme Copper Killer won hands down, I was letting the solvents set in the barrel for a timed 7 minutes. An added bonus that attracted me to the Montana Extreme products is that they are oil bases...how they do that????
I had one 6.5x55 that had a gold plated barrel. I called Montana Extreme and asked a guy that was a very knowledgable about how to best clean the barrel, he said to use one of their plastic brushes with the Copper Killer. Well, I applied the Copper killer to the brush ever 5 strokes for 15 strokes, let it set for 10 minutes, and repeated the process. On the second application, there was no blue on the patches coming out.
For most factory barrels(other than savage) one application(4 wet patches) of the Montana Extreme Copper killer on loose fitting patches will take out all the copper on a 10 minute soaking.
If you are a soaker, then the regular Montana Extreme solvent left over night will get out all the copper.
GM engine cleaner is really great on powder, but if you use it, be sure to use rubber gloves.