Cooking off
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Cooking off (or thermally induced firing) is unfired weapon ammunition exploding prematurely due to heat in the surrounding environment.[1][2] The term is used both for detonation of ammunition not loaded into a weapon, and unintended firing of a loaded weapon due to heating.
A fast cook-off is a cook-off caused by fire. A slow cook-off is caused by a sustained thermal event less intense than fire.
A cooked-off round may cause a
Artillery
Inherent design flaws in early 17th century Swedish leather cannons led to the gun tube overheating which prematurely ignited the gunpowder, injuring the loader.
Muzzle-loading cannon on merchant and naval vessels of the Age of Sail would fire if the vessels caught fire while the guns were loaded. Examples include the merchantman Earl Fitzwilliam and HMS Queen Charlotte.
After the cooking off of
Machine guns
Cooking off is a characteristic of certain air-cooled
Cook offs in machine guns are prevented by:
- Cased cartridge case acts as a heat sink protecting the propellantfrom chamber heat. The case must first be brought up to temperature before the propellant inside can burn.
- automobile engine), or exchanged periodically. Most modern infantry machine guns (GPMG, general-purpose machine gun) are issued with several quick change barrels that are swapped out allowing one barrel to cool while the gun fires with the other.
- Open bolt: Most modern infantry machine guns (and submachine guns) fire from an open bolt, meaning the bolt remains to the rear when the trigger is released. Pulling the trigger releases the bolt forward and fires the weapon simultaneously. Assuming proper operation (no stoppages) a cook off is not possible with this design because a cartridge is not chambered until the moment the trigger is pulled and the weapon is fired, thus there is nothing in the chamber.
Closed bolt
Most modern infantry
Caseless ammunition
Tanks
Cooking off is a serious hazard to crews in damaged and disabled
Missiles and air-dropped bombs
The risk of aircraft armament cooking off is a significant hazard during pre-flight operations, especially for
A different sort of cook-off event was the trigger for the 1969 explosion and fire aboard the USS Enterprise (CVN-65), which also involved a Zuni rocket. During this event, the exhaust from an MD-3A "Huffer" Air Start Unit (ASU) overheated the warhead of a Zuni that was mounted on a parked aircraft, causing it to cook off. As with the Forrestal disaster, this led to procedural and equipment changes, specifically regarding ASUs.
See also
References
- ^ "to cook off". Oxford English Dictionary (Online ed.). Oxford University Press. (Subscription or participating institution membership required.) (verb, search for "to cook off")
- ^ "cook-off". Oxford English Dictionary (Online ed.). Oxford University Press. (Subscription or participating institution membership required.) (noun, 2)
- ^ Chemical and Physical Properties of Nitrocellulose
- ^ Colt Canada OPERATORS INSTRUCTIONS C7 FAMILY OF COMBAT WEAPONS stating at page 7; "The C7 family of weapons can fire the entire combat load of 150 rounds at any rate of fire without danger of cookoff." Archived July 8, 2011, at the Wayback Machine