Aero Precision APRH100822C: Each PRO AR15 barrel is cold hammer forged from 4150 CMV and receives a melonite finish to provide an extremely durable and corrosion-resistant barrel for your next build. These barrels also feature a single-point dimple which creates a solid bedding surface for your gas block set screws and aids in gas block indexing. About Cold Hammer Forging Cold hammer forging differs from other common barrel manufacturing processes. Rather than drilling a blank and using cutters, buttons, and reamers to machine the chamber and rifling into the barrel, a cold hammer forged barrel is made by forming the barrel around a mandrel that has the rifling inclusions precision ground into it. This process is referred to as \"cold\" hammer forging because the process is done at room temperature and the metal is not heated.