So, let me hazard a guess, this rifle left Remington sometime after 1942 and the barrel installed after 3-43 on it's receiver. Probably on a Service straight stock and it made it's way into an armory somewhere at some point. during it's life it needed a rebuild and it was given a "Keystone" C-stock and refinish possibly? After all that it made it's way back into service and no longer was needed and then sat unused for decades. The bore is fairly worn out, though it is shiny and no pitting at all. I have no bore gauge to actually measure it's wear but see were the rifling is very worn down.