This upper offers a M4 profile barrel with a 1/9 RH military twist rate. We are using barrels made by Rosco MFG for us. The barrel is made with 4150 Chrome-moly steel. We are using a Cardinal Forged M4 feed ramped uppers. At a length of only 16", and has a 5.56 NATO chamber. We recommend a 55-62gr bullets for best accuracy. The hand guards are single heat shielded carbine Mil-Spec. BOLT CARRIER GROUP AND CHARGING HANDLE ARE NOT INCLUDED!!!