Aero Precision

Aero Precision's M4E1 5.56mm Mid-Length Upper Receiver comes fully assembled, lacking only a bolt/carrier group and charging handle - the two components most often replaced by customizers. "Mid-Length" refers to the gas tube, which is longer than the standard carbine tube to slow down gas velocity and actually improve reliability in cycling. This is actually a carbine upper, available with either a military 14.5" or civilian 16" barrel (see Gun Tech Note below). The core of the M4E1 5.56mm Mid-Length Upper Receiver is Aero's forged M4E1 receiver that combines the looks of a machined receiver with "mil-spec" parts compatibility (including BCG Mfg: Aero Precision.