The .300 AAC Blackout cartridges were developed by Advanced Armament Corporation (AAC) for use in the M4 carbine to achieve ballistics similar to the 7.62x39mm supersonic cartridge, and to offer a subsonic yet powerful cartridge for the AR15 platform as an alternative to the MP5SD 9mm, all while utilizing a standard (STANAG) magazine. The Barnaul .300BLK is a 145-grain supersonic cartridge with a polymer-coated steel case. This is the most affordable .300BLK ammunition on the market today. We recommend using .300 Blackout magazines for optimum performance. Technical Specifications Bullet Type: FMJ Weight: 145 grain Muzzle Velocity (feet per second) 1985 Muzzl Energy (foot-pounds) 1268 Ballistic Coefficient (G1) 366 Max Powder Pressure Bar (lb/inch2) 50,763 Cartridge Max Length 2.15 inches Cartridge Average Weight 239 grain