I found the Railway Rifle as expected in the Bedford Station railway car. Normal difficulty, level 50, PC platform. User:Fredgiblet
I have not found the Railway Rifle next to the skeleton in the blue car, PC version level 12. User:CactusLynx
Can anyone add if this works off the heavy weapon or rifle perk? I assume rifle, but I don't know for sure.
I found a Railway Rifle at level 17, at Big John's Salvage in the hidden bomb shelter there. The note saying it only spawns after level 20 is clearly incorrect. Battlecarrier