300 Blackout is a centerfire cartridge designed to work in AR-15-pattern rifles, optimized for short barrels and for use with subsonic, suppressed loads.

300 Blackout fires a .30-caliber bullet from a case sized to function in standard AR-15 magazines and platforms, and it performs well from short barrels. A defining feature is its ability to run both supersonic loads and heavier subsonic loads that pair well with suppressors. It is used for home defense, short-to-medium-range hunting, and recreational and suppressed shooting; supersonic and subsonic loads behave very differently. An important safety note: 300 Blackout must never be loaded into a 5.56/.223 chamber, as the rounds can chamber and cause catastrophic damage. It suits shooters building short-barreled or suppressed AR-pattern rifles.

General information about this caliber — not a recommendation for this specific firearm.