AT3 Tactical 9mm Straight Profile 8.3 Inch AR-15 Barrel Black. barrel from AT3. Crafted from premium 4150 CrMoV steel per MIL-B-11595E specs and protected by a rugged black nitride finish. The straight profile adds a balanced weight while maintaining accuracy with 9mm ammunition. At just 11? long with 1/228 muzzle threads its an ultra-compact option for dedicated 9mm AR uppers or PDW-style pistol builds. Specifications for AT3 Tactical 9mm Straight Profile AR-15 Barrel: Manufacturer: AT3 Tactical Color: Black Caliber: 9mm Luger Barrel Profile: Straight Gun Make: AR Platform Gun Model: AR-15 Package Contents: AT3 Tactical 9mm Straight Profile AR-15 Barrel What firearm models does the manufacturer say AT3 Tactical 9mm Straight Profile AR-15 Barrel is compatible with? The manufacturer says that AT3 Tactical 9mm Straight Profile AR-15 Barrel is compatible with AR-15AT3 Tactical AT3-9MM-8.3-28: 9mm Straight Profile 8.3 Inch AR-15 Barrel Black