Why do you shake bullets with sand?

Shaking bullets with sand is a method used to clean and polish them. The abrasive nature of the sand helps remove oxidation, dirt, and imperfections from the bullet's surface, improving its appearance and potentially enhancing its performance. This process is often employed by reloaders and hobbyists to maintain the quality of their ammunition. However, care must be taken to avoid damaging the bullets or altering their dimensions.