A semi or fully automatic firearm is said to fire from an open bolt if, when ready to fire, the bolt and working parts are held to the rear. When the trigger is pulled the bolt goes forward, feeding a round from the magazine (or belt) into the chamber and firing it. Like any other self-loading design without an external power supply, the action is cycled by the energy of the shot; this sends the bolt back to the rear, ejecting the empty cartridge case and preparing for the next shot (or continuing forward again, if the trigger is held down and the weapon is an automatic). Generally, an open-bolt firing cycle is used for fully automatic weapons and not for semi-automatic weapons (except some semi-automatic conversions of automatic designs). Firearms using Advanced Primer Ignition blowback inherently fire from open bolt only.
Open bolt
Questions and Answers
Q: What is an open bolt in firearms?
A: An open bolt in firearms is a firing mechanism in which the bolt and working parts are held to the rear when ready to fire. When the trigger is pulled, the bolt goes forward, feeding a round into the chamber and firing it, and then ejecting the empty cartridge case.
Q: What types of firearms use an open-bolt firing cycle?
A: Generally, fully automatic weapons use an open-bolt firing cycle. Some semi-automatic conversions of automatic designs also use this mechanism.
Q: How is the open-bolt firing cycle cycled?
A: The action of the open-bolt firing cycle is cycled by the energy of the shot. This sends the bolt to the rear, ejecting the empty cartridge case and preparing for the next shot.
Q: Can semi-automatic firearms use an open-bolt firing cycle?
A: Semi-automatic firearms do not generally use an open-bolt firing cycle except for some semi-automatic conversions of automatic designs.
Q: What is the function of the open-bolt firing cycle?
A: The function of the open-bolt firing cycle is to feed a round from the magazine or belt into the chamber, fire it, eject the empty cartridge case, and prepare for the next shot.
Q: Are all firearms with an open bolt fully automatic?
A: No, not all firearms with an open bolt are fully automatic. Some firearms using Advanced Primer Ignition blowback inherently fire from an open bolt only.
Q: Does the open-bolt firing cycle require an external power supply?
A: No, the open-bolt firing cycle does not require an external power supply. The action is cycled by the energy of the shot.