Though you've done a good job with the pictures, it's hard to say without seeing it for real, so some random thoughts:
1) Shoot it. If it's deemed safe by a qualified gunsmith, try her out. The colors indicate fouling, but that's to be expected for a gun that probably went to war, had hundreds of rounds fire through it, and was cleaned by a guy who really didn't want to be there. Storage practices weren't always the best, either.
2) Decide what is acceptable to you. If you shoot it, and you are hitting paper, decide if it's enough for you. If you are expecting sub MOA hits at 500 meters, you may be asking too much. These are great rifles captured in a period of time before chrome lined, laser cut, computer approved barrels.
From what I can see, the bore looks decent. I would try some Windex, since alot of surplus ammo is corrosive, run a dry patch, and then some Break Free.
Other guys have other methods, but that has always worked for me, my friend.