Developed by the US Advanced Armament Corporation (AAC), the .300 AAC Blackout round was originally designed to be used in the M4 Carbine. Commonly referred to as just .300 Blackout, the round’s purpose is to be similar to the 7.62x39mm while using AR-15 magazines in their normal configuration. The 300 Blackout (300 BLK) round is the hottest thing on the suppressor community right now! 300 Blackout ammunition puts a 30 cal projectile in your AR-15 platform using the same AR-15 magazines. 300 Blackout now grants the ability to run a subsonic load reliably in a semi-automatic AR-15.