The lack of hot water at the front is one of the reasons so many WW2 rifles have black and pitted bores from corrosive primers. The battle rifle is an expendable piece of equipment, kind of like the ammunition is. Soviet ammo in WW2 was pretty corrosive and they continued to make it that way for years afterwards. The US changed to non corrosive earlier and that ammo is probably all gone now. Some foriegn "surplus" ammo may still have corrosive primers in it if they are older shells. Rifles that have a nice clean and shiny bore from WW2 either were not fired with corrosive ammo (very doubtful for Soviet equipment) or are arsenal rebuilds with a fresh barrel.
My M1 garand that I had was a Korean war return and when I got it I saw that the barrel was dark and pitted. It was headspaced OK so was safe to shoot but as long as I had it I would never plan on any great accuracy. My guess is that it would hit a full size silhouette at 100 yards but anything farther was a crap shoot. I figured it was minute of elephant accuracy.
