The K9 12.5 features a proprietary patrol-length gas system that is smoother than a carbine length and more reliable than a mid-length. Because this is the optimal amount of gas, the barrel performs reliably whether suppressed or unsuppressed. The K9’s continuous taper profile is a proven design from the past, ideal for dissipating heat during hard use. It also includes an updated target crown carried over from the Purebred series. This crown has no 90-degree cuts, which improves harmonics, fit, and finish. NOTE: COMES WITH PATROL LENGTH GAS TUBE.