AR 15 (M16/M4)

The heart of the Colt AR-15 is the direct gas system. This system uses no conventional gas piston and rod to propel bolt group back after the shot is fired. Instead, the hot powder gases are fed from the barrel and down to the stainless steel tube into the receiver. Inside the receiver, the rear end of the gas tube enters into the "gas key", a small attachment on the top of the bolt carrier. The hot gases, through the gas key, enter the hollow cavity inside the bolt carrier, and expands there, acting against the bolt carrier and the collar around the bolt body. The pressure of the gases causes the bolt carrier to move back against initially stationary bolt. The M16 clone CQ/Terab has been observed in South Sudan used by some rebel groups.The CQ is a variant of the AR-15 rifle manufactured by the Chinese arms company, NORINCO. The "Terab" rifle is a clone of the Norinco CQ manufactured by the MIC (Military Industry Corporation) of Sudan. The "Armada" rifle is a clone of the Norinco CQ manufactured by S.A.M. - Shooter's Arms Manufacturing, a.k.a. Shooter's Arms Guns & Ammo Corporation, in the Philippines. The CQ/Terab has been observed in South Sudan used by some rebel groups in 2013.