Our 5.56 chambered 16 inch Government Profile Mid-Length Modern Series Barrel is machined from 4150 Chrome Moly Vanadium steel with a QPQ Corrosion Resistant Finish and QPQ coated M4 feed ramp extension. Weight 28oz Length 16 Profile Government Twist 1:7 Finish QPQ Corrosion Resistant Material 4150 CMV Thread Pitch 1/2x28 Caliber 5.56 NATO Feed Ramp M4 Flutes N/A Gas System Midlength Rifling Conventional Gas Block System 0.750