AT3 Tactical 300 Blackout Medium Profile 6 Inch AR-15 Barrel Black. 5 Inch .300 Blackout Barrel makes a great choice for your short heavy-hitting pistol or SBR AR-15 builds. Made from 4150 CMV steel per Mil-B-11595E and finished with a durable black nitride treatment this barrel holds up under pressure with excellent corrosion resistance. This barrel fits all your standard AR-15 uppers if youre going for a fresh build with M4 feed ramps for reliability. Specifications for AT3 Tactical .300 Blackout Medium Profile AR-15 Barrel: Manufacturer: AT3 Tactical Color: Black Caliber: .300 AAC Blackout Barrel Profile: Medium Gun Make: AR Platform Gun Model: AR-15 Package Contents: AT3 Tactical .300 Blackout Medium Profile AR-15 Barrel What firearm models does the manufacturer say AT3 Tactical .300 Blackout Medium Profile AR-15 Barrel is compatible with? The manufacturer says that AT3 Tactical .300 Blackout Medium Profile AR-15 Barrel is compatible with AR-15AT3 Tactical AT3-300-6: 300 Blackout Medium Profile 6 Inch AR-15 Barrel Black