The simple blowback mechanism typically consists of the bolt which rests against the base of the cartridge case and a recoil spring that resists the kinetic energy of the bolt when it is thrown back in recoil and then drives the bolt back forward into firing position.
The simple blowback mechanism typically consists of the bolt. This bolt rests against the base of the cartridge case. This bolt rests against the base of a recoil spring. This recoil spring resists the kinetic energy of the bolt when it is thrown back in recoil. This bolt then drives the bolt back forward into firing position.