This Rosco 16″ M4 5.56 NATO Bloodline Barrel is the perfect upgrade for your next build, offering ideal balance and properly sized gas ports to maximize performance and reduce premature wear from over-gassed barrels. Rosco 5.56 (NATO) barrels are built to meet the needs of modern carbine shooters. We’re a long way from our daddy’s Sporter AR, and those old specs just won’t cut it anymore. From managing dwell times for SBRs to running suppressors or setting up a balanced patrol carbine, Rosco has incorporated your needs into their engineering. They achieve this by choosing the right twist rates, gas port sizes, and barrel materials tailored to each barrel. Rosco also considers input from both consumers and military end users to deliver the rifle barrel you need, not just the one they want to sell.