Re: INTERNAL barrel rust? can you remove it all?
Sorry I didn't specify. Rust (the subject of the OP) and ''light copper and carbon'' comes right out with a dry brush. Really heavy copper fouling in barrels that have 300-400 hundred rounds through them before cleaning, takes a strong solvent. I like M-Pro 7 products. Just don't let their copper solvent sit on blued surfaces. Their copper solvent only took 2 apps to remove heavy copper deposits from a grossly neglected barrel. After I dry-brushed it a few times, I just mopped it in, let it soak 10 minutes, brushed it 5 passes in each direction and swabbed it out. Good stuff. Better than all the rest I've tried. Rust alone is easy to remove if it is dry. Give dry brushing a try. It really gets out a lot of dust. Again, anything wet also acts as a lubricant. Those spiral loop brushes clean the lands well too. They don't get a thing out of the grooves though.
Happiness is a fine Mauser build.