This is Hornady Subsonic .300 Blackout 190-grain ammo with the Hornady Sub-X bullet.
Hornady 300 Blackout Subsonic Ammunition is designed for accuracy and performance below the speed of sound. The new 190 gr 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 hollowpoint cavity to help it expand reliably at low velocities.