Tinker,
I have no idea how tin would react to being fired from a barrel but the terminal ballistics would not be good. As a material it is much too brittle. It cannot be drawn and would have to be cast. The melting point is very low, around 230C. Lead is a good 100C higher than that. Current prices per lb are about US$1.00 for lead, US$3.00 for copper and US$7.60 for tin.

4seventy,

What puzzles me about OSR is that it is more difficult to see than what general wear and tear seems to be. There also seems to be no evidence that any particular type of bullet causes OSR. It has been seen on rifles that have fired some monos and it has been seen on rifles that have not fired monos.

Does anyone know when OSR was seen for the first time?

If it cannot be dimensionally measured then it is a cosmetic affliction, the same as a scratch or dent on the stock or barrel. Use it often enough and it will happen.

If it can be dimensionally measured, is it of a greater magnitude than normal wear of the lands and grooves? That can easily be measured and I often do so to tailor bullets to the bore of odball sized barrels.