According to this web site, you can make your own electro- bore cleaning kit without much of an investment.
http://www.surplusrifle.com/reviews/copperout/index.asp
I had an M1 Garand rifle with a bore that looked completely hopeless. I cleaned it as well as possible using Hoppe's #9 Bore Cleaner and a bronze bore brush. No matter how much I scrubbed it, it still looked awful.
On a whim, I entered an NRA sanctioned High Power match and used it. I was amazed that after the match was over, the bore was in near perfect condition. (I did not win, but did respectable.)
So you might try cleaning it as best you can, and then do some shooting with it just to see what it looks like after it has been shot. (Just a thought)
Mauser720 - Ron