The Hornady Sub-X (Subsonic - eXpanding) bullet features a lead core. Long grooves in its gilding metal jacket combine with the bullet's flat profile and the patented Flex Tip insert within its hollow-point cavity to help it expand reliably at low velocities. Performance meets or exceeds FBI Protocol terminal ballistic test requirements. Features:a Designed to expand at velocities down to 900 fps.a Bullets feature a cannelure for a positive case crimp for use in semi-autos.a Designed specifically to fit, feed, and function in a variety of firearms including gas system guns.