Cooking off
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Cooking off (or thermally induced firing) refers to ammunition exploding prematurely due to heat in the surrounding environment.
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[edit] Artillery
Inherent design flaws in early 17th century Swedish leather cannons led to the gun tube becoming deformed which prematurely ignited the gunpowder, injuring the loader.
After the cooking off of artillery shells in the G-5 field gun in the late 1980s, the South African Army changed commands from "cease fire" to "cease loading". This allowed crews to fire any loaded shells to prevent them from heating up and exploding.
[edit] Caseless ammunition
Caseless ammunition eliminates the metal case that typically holds the primer or igniter and the explosive charge ("gunpowder") that propels the bullet. The metal case absorbs a large portion of the waste heat of firing. Ejecting this hot, empty case removes that heat from the weapon. With caseless rounds, other means of reducing waste heat are necessary, especially in automatic fire.
[edit] Grenades
Cooking off also refers to the practice of waiting a few seconds before throwing a grenade after starting the timer (typically done by pulling the pin and releasing the handle(also known as the 'spoon')). This enables the thrower to achieve a lethal air burst over a target or provides the least opportunity for the target to throw the grenade away or back at the thrower.
[edit] Rifles
Cooking off is a characteristic of certain machine guns, especially those firing from a closed bolt, that are air-cooled, and capable of sustained use. When the trigger is released, the weapon feed leaves a final round in the chamber, where heat ignites the propellant firing the round. Cooking off limits the rate of fire of many rifles, since heavy use will heat up the gun's barrel.
In the case of the US M296 or some other squad assault weapons sustained fire of only a few hundred rounds per minute can create sufficient heat. Inefficient or insufficient cooling of the barrel or chamber can cause either a cook off or stoppage of the gun through metal expansion.
[edit] Tanks
Cooking off is a serious hazard to crews in damaged and disabled tanks. Attempted solutions include storing ammunition under water and insulating ammunition compartments. The current technique, used in tanks like the M1 Abrams, is to armor the compartments and provide blow-off panels to channel the force of the explosion to the exterior of the tank.de:Cook off
