This Rosco 16" 5.56 Heavy Barrel (HB) is built for end users who need to push their guns hard without hesitation. The heavy contour barrel is ideal for full auto use and abuse. Rosco 5.56 (NATO) barrels are designed to meet the needs of modern carbine shooters. We're a long way from our dad's Sporter AR, and those specs just won't suffice anymore. From carefully managed dwell times for SBRs, to suppressed firing, or setting up a balanced patrol carbine, Rosco has incorporated your needs into their engineering. Rosco has achieved this by selecting the right twist rates, gas port diameters, and barrel materials for each barrel. Rosco also considered input from their customers and military end users to provide the rifle barrel you need, not just the one they want to sell.