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 weapons. Patented Flex Tip technology aids in expansion at velocities as low as 900 fps Meets FBI protocol for terminal ballistic test requirements Lead core bullet with cannelured jacket provides positive case crimp for use in semiautomatics Designed to fit feed and function in a variety of firearms including gas system guns