A .223/5.56 300 Blackout bolt carrier group gives you the flexibility to run multiple calibers from the same AR-15 lower. At Daytona Tactical, we carry .223/5.56 300 Blackout bolt carrier groups built to cycle reliably across .223 Remington, 5.56 NATO, and 300 Blackout with the right upper configuration. Browse our in-stock BCG selection from trusted brands at competitive prices with fast shipping across the USA.