The MG 34 fires from an open bolt and this format both keeps the barrel open at both ends after firing ceases, allowing airflow through it and helping it to cool faster, and meanwhile retains the next unfired bullet outside the chamber until the trigger is squeezed again; and thus the cartridges are protected from the risk of cook-offs from high chamber temperatures after long bouts of sustained automatic fire. The firearm was designed with a rotating bolt operated by short recoil aided by a muzzle booster. When the firearm is ready to fire the bolt is pulled back to the rear and is held back by the sear. With the pull of the trigger the sear disengages sending the bolt forward under pressure from the recoil spring. A cartridge is stripped from the magazine or belt and the round is pushed into the chamber. As the bolt moves forward into battery the bolt rotates engaging the locking lugs and chamber locking the bolt to the barrel. The striker strikes and ignites the primer and the round is fired. The recoil causes the barrel and bolt to move backwards a short distance. The rearward movement of the barrel causes the rotating bolt to rotate back disengaging the locking lugs and unlocking the bolt from the barrel. The barrel returns to its forward position while the bolt recoils to its rear position. The empty casing is ejected and the cycle can begin anew.