cleaning bore

[Bounty Hunter]

i have acquired an old sako 222 mag. the man who owned it has been gone foe thirteen years, so that means that it hasn't been cleaned in at least that long and probably longer, the outside looks great but the barrel looked awfully dirty, so i started. i've never seen fouling like this. i'm on my second day with a trash can full of blue-green patches and it is getting a little bit better but not much. i'm using shooters choice and blue wonder. i think i'm on my third brush, i've even gone to a .243 brush to get more scrubbing action. has anyone ever seen one this bad and what might i do to speed up the process.

thanks

B H