This bloodline barrel (mid-length): 14.5" m4 5.56 nato mid-length barrel was designed around the usasoc specs for an improved upper receiver group with a little bit of the rosco touch as well.The longer gas system allows for a smoother gas curve which leads to managed dwell times.This combo creates a great balance of speed and performanceLength: 14.50"Model: BloodlineTwist: 1:7"Finish: NitrideBarrel Type: Mid-Length