Originally Posted by Lefty7mmstw
Now for the really funky part; some calibers like the 7rum can basically "bake in" carbon and copper fouling. Some of the milder solvents( or copper specific) are not able to get all of it out without a serious fight. If I'm not mistaken, sweets is very good at pulling copper, somewhat like barnes is. You also have to go to a carbon specific solvent like hoppes or kroil to take out the baked in carbon. It's a bit like scouring the coating off of a cast iron. Leave her soaked overnight with a creeping oil like kroil and you'll get even more out when you take a bronze brush after it again. You have a fouled barrel, and if the throat is good, it should wake up after you finally get it clean.
I never start with a dry brush(at least a bit of hoppes) as dry brushes can accelerate wear(using fouling to sand the bore) and this cal. already beats the hell out of the barrel; you don't need cleaning to add wear.
I am in agreement with Lefty, Powder solvents are the way to go. Hoppes #9 is probably the best powder solvent out there. Shooters Choice is right there too. these solvents, as long as they are ammonia free, can be left in the bore over night. I leave have to soak my 7 STW over night to get the powder out of it....
Kroil works really well too, but must be left in the bore for at least 24 hrs to creap under the fouling. After that it's easier to knock the carbon out.
this is an extreme case, so I'd also reccomend using non-embedding, J-B bore paste with a tight patch to address the carbon as well. Follow the directions very carefully and don't over use it.
When I saturate my bores for overnight soaking, I run at least 2 patches with the muzzle pointed slightly down so the solvent doesn't creap or drip back into the action and into the trigger housing. This is where gun vises or cradles are awesome.
I will also use a saturated brush for cleaning being careful while letting it exit the barrel as to not mess up the crown.
I use combination of these solvents and methods (not mixing solvents) but going back and forth between methods as necessary to get the barrel clean.
Once you get the barrel clean it will be easier to get it clean the next time if you run a pach saturated with Kroil down the bore and leave it for an hour or so, then run two dry patches to remove the excess. It will go into the "pores" of the steel and help keep the carbon fouling from sticking as much.
Hope this helps, it's what I do and works for me.