How to explain very old paper shotgun shells that aren't swelled and their roll or star crimp isn't pushed out? You open the shell and the shot is heavily oxidized-carbonated and often kind of all together in one clump with the surface compounds filling spaces between the shot.
Good question. Please remember that lead forming an oxide and a carbonate are two very different reactions. I assume you have heard about old paper shells swelling to the point that they can't be chambered? I certainly have. So how much expansion would it take before tightly packed oxidized lead shot split a gun stock? When surface compounds fill all the spaces between the shot, what happens next? Can you say for certain that all of those lead oxides are so loosely bound they actually move into those empty spaces? I couldn't tell you for certain whether shot in a waxed paper shell oxidizes at a slower rate than shot packed into a large hole in a shotgun buttstock. I can't tell you what conditions might accelerate this destructive process, or even how long it takes to damage a gun stock. All I know for certain is that I have seen it several times, and the result was a mass of slightly enlarged shot and a split gun stock. In the case of the G Grade Lefever I repaired, it was enough to visibly force the buttplate outward. In the Gunbroker auction photos, there was an obvious gap between the buttplate and the end of the stock... along with equally obvious splits along both sides of the shot filled cavity.
If you think that sort of damage would have occurred without the presence of heavily oxidized lead shot being stuffed into a hole under the buttplate, well that's OK. I can't force you to believe that which I have seen and touched and repaired. But I know I won't be putting loose lead shot into any of my gun stocks.
