Most people think of the arms race as a competition occurring between the U.S. and the former Soviet Union during the Cold War. However, the struggle of nations to exert superiority over their enemies by amassing more and better weapons has been an ongoing reality for eons. The lowly bullet is no exception. The earliest ammunition consisted of small round stones, but these had little effect on armor-covered warriors. This led arms manufacturers to explore metal bullets, made by pouring molten metal into a mold and letting it harden.
Iron balls were popular for a while, but they were difficult to make, required extreme temperatures to melt and often ruptured the musket barrels trying to fire them. Then, in the early 1600s, lead balls started flying over battlefields. Lead had a low melting point, so it could be cast in a ladle over a wood fire. Soldiers and hunters could resupply their ammunition while they cooked dinner. And because they were softer, lead balls posed little risk of damaging gun barrels. These bullets, also known as musket balls or "rounds," would reign supreme until the 1800s and the development of an aerodynamic projectile.