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. - Our BarnauL .300BLK available now is a 145-grain supersonic cartridge with a polymer-coated steel case. This is the most affordable .300BLK ammunition on the market today. - A .300BLK subsonic cartridge is a heavy lower-velocity round perfect for pairing with a suppressor. Using subsonic cartridges with a suppressor helps to eliminate the crack that is inherent with supersonic cartridges reducing noise levels down to a safer volume. - We recommend using .300 Blackout magazines for optimum performance. - Ballistic Coefficient (G1): 0366 - Muzzle Velocity V0 ft/sec: 1985 - Muzzle Energy E0 J ft/lb: 1268 - Max Powder Pressure Bar (lb/inch2): 50763 - Cartridge Max Length: 2.15 inches - Cartridge Average Weight: 239 grains - Rounds per Box: 20 - Rounds per Case: 500