Does anyone know when this took place? I restored my father in laws old Winchester pump that has a totally toasted barrel interior. Only thing I can figure is that he shot corrosive primers in it and never cleaned it.
The problem with corrosion in .22LR firearms was directly related to corrosive priming.The nitro source for smokeless powder was corrosive until around 1960. So clean bore priming only solved part of the problem.