I am always amazed at how most guns in this age of non-corrosive primers survive in good shape even though cleaned little, if at all.
Several years ago I bought, for a good price, a 6" Model 19; the bore was leaded up so bad it probably measured .32" land-to-land in the bore.
When I got it home, I must have scrubbed that bore for 2 solid hours to get all the crud out, particularly at the forcing cone.
The final result was gratifying - the bore was in perfect condition. A few drops of preservative oil on a patch finished the job, and I'm happy.
I also recently bought a beater Japanese Type 94 pistol (you know, the worst pistol ever designed) so that I could photograph it for a future article in Dillon's Blue Press. The bore was really filthy, probably last fired with WWII ammo. A bristle brush and some Hoppe's revealed a really nice bore (not that I'll ever fire it). I was pleasantly surprised.
The only time I was ever stung was on a U.S. Model of 1917 rifle - the bore was "cloudy" as far as I could tell at the dimly-lit gun show. But it was one of the rarer Winchesters, and I added it to my collection. After thorough scrubbing, the cloudiness was diagnosed as minor pitting. Suprisingly, the gun turned out to be pretty accurate in spite of the pits. Guns from the days of corrosive ammo do need to be examined critically. Modern guns' bores - not so much.
John