300 Blackout was built to give the AR-15 platform 30-caliber performance from short barrels — and to run quiet. Supersonic 110 to 125 grain loads deliver solid terminal performance for hunting and range work, while heavy 190 to 220 grain subsonics pair with a suppressor for hearing-safe shooting. Both feed from standard AR magazines with only a barrel change, which is exactly why the cartridge took off.