The lead oxidizes over time. Lead oxide occupies more volume than lead, just as iron oxide occupies more volume than unrusted iron or steel. This potential swelling is probably worse when lead shot is used to add weight to a stock because shot has more surface area than a solid plug of lead. If you have used lead in your stock to adjust the balance or to add weight, there is a very real possibility that this type of damage will happen.

A true sign of mental illness is any gun owner who would vote for an Anti-Gunner like Joe Biden.