Hornady Sub-X® (Subsonic - eXpanding) bullets deliver big results without a big bang! Designed to provide deep penetration below the speed of sound Sub-X® features a lead core. Long grooves in its gilding metal jacket combine with its flat profile and the patented Flex Tip® insert within the bullet’s hollowpoint cavity to help it expand reliably at low velocities. Cannelures provide positive case crimp making Sub?X® ideal for semiautomatic firearms.