eli5: How does a gun backfire? isn’t there any mechanism in place to prevent it from happening?
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When a gun is loaded, a cartridge (round of ammunition- bullet attached to shell casing full of powder) is inserted into the *chamber* (rear end of the barrel). It’s held in place in the front by the shape of the barrel, and in the rear by a part called the bolt. The bolt has to be snug against the back of the shell casing because when the powder explodes, it will push the bullet forward but also push the shell casing backwards.
The thin brass shell casing itself isn’t strong enough to contain the pressure of the exploding powder. The thick steel barrel which is snug around the casing and the thick steel bolt which is snug behind it reinforce the shell casing and keep the high pressure of the exploding powder contained. Only the bullet is able to move, and move it does.
However if the loading malfunctions, the cartridge can be loaded with the bolt *out of battery*. That means the bolt is not fully locked in behind the cartridge. So when the powder starts to burn, it will push the bolt back and push the shell casing out of the barrel. That leaves only the thin brass containing the high pressure (35,000 PSI or more), and the thin brass isn’t up to that task. Thus the brass breaks open, and you get a boom facing sideways or backwards. Or, the bolt is pushed backwards with great force and the rest of the gun shreds itself.
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