This is a Ballistic Advantage Barrel known as the Modern Series chambered in 556NATO, model BABL556024M.
This 5.56 chambered 12.5 inch Government Profile Modern Series Barrel is machined from 4150 Chrome Moly Vanadium steel with a QPQ Corrosion Resistant Finish and QPQ coated M4 feed ramp extension. All NFA/ATF Rules Apply. You may use this barrel with a lower receiver that is a Registered SBR" Machine Gun" or Pistol. Possession of this barrel along with a Non-NFA lower receiver is Prohibited" except when installed on a Pistol configuration firearm
Features:
Length: 12.5";Material: 4150 Chrome Moly Vanadium;Profile: Government;Finish: QPQ Corrosion Resistant;Gas System Length: Carbine;Gas Block Journal: .750
Twist Rate: 1:7 inches
Muzzle: 1/2x28 Threaded
Weight: 22 oz