G&G M4 Blow back - Black Version 1.2 G&G M4/M16 Series- • Metal Upper Receiver • New Black Nylon Fiber Lower Receiver M4 Blow back- C.A.S. has re-modeled the G&G M4 blow back with a metal upper receiver AND a functioning spring tension release forward assist knob. The spring tension release function allows you to store your rifle without any tension on the main spring. This ensures that your rifle is never going to lose great amounts of power due to the main spring remaining compressed for any amounts of time. The new G&G blow back line is not what you would typically think for a traditional “blow back”. One might usually hear ‘blow back’ and think of a pistol with its great cycling noise, and hard recoil. Though the G&G blow backs do have some faint cycling noise, there is little to no recoil felt. This operation is entirely designed for appearance. Differing from typical blow back rifles, G&G uses its own air compressed in the chamber to help power the ejection port back and forth with each shot, semi or full auto. Differing from gun to gun as to how far back the ejection port flies open is due entirely to the top blow back portions varying air seal (*this does not affect the main portion of the gearbox’s air seal, or it’s shooting performance). To get the most blow back action out of these guns, there must be a BB in the chamber to add extra assist to the operation. All in all, with the same performance as the traditional G&G guns, the blow back line is sure to be popular amongst those seeking the most realistic appearing operations possible. These guns come stock with metal bushings and a customized black gearbox for the Canadian market. Typical velocity ranges between 340-360 feet per second. Battery, charger, safety glasses, and a sample pack of 1000 high grade G&G BB’s come standard with the package.