16 inch 5.56 NATO Carbine Length 1/7 Twist 4150 CMV Melonite Barrel, Medium Contour Profile. These high quality barrels are made by Kak Industry, melonited/nitrided correctly before barrel extensions are installed and gas ports drilled. Weight 2 Length 16 Profile MEDIUM Twist 1:7 Finish Melonite Material 4150 CMV Thread Pitch 1/2-28 Caliber 5.56 NATO Feed Ramp M4 Flutes N/A Gas System Carbine Rifling Conventional Gas Block System 0.750