Perfect for building your custom Mk4 upper group. Comes with properly installed M4 barrel extension. All barrel sub-assemblies are properly head spaced. Made of 4140CM with a SBN Finish.

Features :

• 1:16 Twist 4140 Chrome moly
• 1/2X28 thread pitch
• Medium taper profile
• ,Carbine length gas port .750" gas block Journal,