In simple blowback operation, the empty cartridge situation is hurled backward by the explosion from the cartridge and thus pushes back again the bolt, or breechblock, which consequently compresses a spring and it is returned for the firing placement on that spring’s recoil. The basic issue linked to blowback is https://machguns.com/product/american-180-tuned-by-val-cooper-excellent-w-extras-b01787/