Delayed Blowback

(dĭ-lā′)   (blō′băk′)

A variant of the blowback principle in which the blowback operation is by some means retarded (e.g., by a fluted or grooved chamber). For more powerful rounds or for a lighter operating mechanism, some system of delayed or retarded blowback is often used, requiring the bolt to overcome some initial resistance while not fully locked. Because of high pressures, rifle-caliber delayed blowback firearms, such as the FAMAS and G3, typically have fluted chambers to ease extraction.

Gun Gas Delay Blow Back
Gun Gas Delay Blow Back