From musket balls to modern rounds, this Spark documentary traces the engineering history of the bullet. It covers the invention of rifling that stabilized shots in flight, the design of hollow-point rounds meant to expand on impact, and the armor-piercing .50 caliber round built to punch through vehicles. Forensic experts explain how ballistics analysis matches a fired bullet back to the specific gun that fired it, using microscopic marks left on the casing and slug. The film then turns to current research into guided small-caliber ammunition, including projectiles designed to correct their own trajectory mid-flight, and defensive systems built to intercept incoming rounds or missiles rather than kill a target. Interviews with engineers and ballistics specialists carry the explanation, paired with slow-motion footage of rounds firing and archival material showing older weapons in use. The throughline is a shift in purpose, from ammunition designed purely to be lethal at range toward technology aimed at precision and protection.