Perfect for building your custom AR15 upper group. Comes with properly installed M4 barrel extension. All barrel sub-assemblies are properly headspaced.

• 16.1?
• Medium Taper Profile
• 4140 Chrome Moly
• Salt Bath Nitride Finish inside and out
• 1:7 Twist
• 5.5645 NATO Chamber
• Threaded 1/2-28
• Midlength gas port
• .750? Gas Journal