Bloodline 7.5 M4 5.56 NATO: This Rosco 7.5 M4 5.56 NATO Bloodline Barrel is designed to be the perfect addition to any SBR or Pistol build. This barrel was designed to perform suppressed and be accurate. ALL NFA RULES APPLY!Our Rosco 5.56 (NATO) barrels are designed to meet the modern-day carbine shooters requirements. We are a long way from our daddy's "Sporter" AR, and those specs just won't cut it anymore. From properly managed dwell times for SBR's, to running suppressed, or setting up a balanced patrol carbine we have incorporated your needs into our engineering. We have successfully accomplished this by selecting the right twist rates, gas port diameters, and barrel materials according to the barrel we are making rather than a one-size fits all approach. We have also balanced input from our consumers and military end users to bring you the product you need, not just the one we want to sell you. Barrel Length 7.5" Barrel Weight 17.28 Oz Barrel Material 4150 CMV Barrel Caliber 5.56 Barrel Profile M4 Twist 1/7 Barrel Thread 1/2 x 28 Gas Block Size .750 Gas System Length Pistol Barrel Crown 11 Degree Barrel Finish Nitride Barrel Extension Finish Nitride