Pro2a Tactical's unique line of 300 Blackout AR-15 NR Side Charging Upper Assemblies. 300 Blackout uses the same BCG and magazines as 223/5.56 and is the perfect caliber for short/medium range applications and is the perfect round to be suppressed. We offer the 300 Blackout in a variety of barrel lengths, twists and formats to suit your needs. All of our NR Side Charging uppers are assembled by the most experienced armorers and covered by our limited lifetime guarantee.