Guns don’t kill people; people don’t kill people; bullets kill people. As the nation debates, again, the best way to curb gun violence, many of the questions focus on the firearms themselves. But an equally important consideration is ammunition. Roughly 10 billion rounds are manufactured in the US each year, with a weight equal to two Titanics. More to the point, it’s enough bullets to pump 32 rounds into every man, woman, and child in America.

From the musket ball to the .45 Colt cartridge to the .223 shells used in the Newtown massacre, the story of ammunition is in many ways a familiar tale of technological progress, as bullets have become cheaper, easier to use, and often more deadly. But this engineering success has become a social and moral crisis. Here’s a data-driven examination of the bullet: its variety, its spread, and the policies that might help curb its lethal consequences.