What Happens When You Throw Bullets into Molten Aluminum?

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What happens when you put live ammunition into molten aluminum? The answer shouldn’t be too hard to imagine. It is going to go boom. The only question is, really, how big of a boom. Enter The Backyard Scientist.

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Is this actually science? By YouTube’s standards, yes. Hell yes. This is the heart of science. But don’t expect you’re science professor to ask you to repeat the experiment in the lab. This one needs some outside space.

And though it is science, there are two principles at work that are givens. The temperature of molten aluminum will be sufficient to ignite the primer, which will ignite the powder inside the case.

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Every cartridge has a temperature at which it will “cook-off,” a phrase that simply means it will ignite without being struck by a firing pin. This can happen in the chamebr of a gun that hasn’t cooled down (as in sustained automatic fire) or in a campfire (should you just drop the cartridges in).

The second thing is that the bullet–the actual projectile–isn’t going to go rifling off into space. It may travel a good distance, but it will not have the controlled propulsion it would have from a closed system (like a rifle barrel) to maximize the energy of the explosion.

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To prove this, he cooks one with a torch until it pops.

Rounds that explode outside of guns typically just rupture dramatically as the thin walls of the brass case (usually supported by the chamber of a gun) are easier for the explosion to tear through.

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So–now onto the science. Why molten aluminum? I’m not sure. Why .22 LR ammo? That one is easier to answer. These small cartridges are readily available, and reasonably light on powder, which means a smaller explosion. The Backyard Scientist had more to fear from burns from the splashing aluminum than the whizzing projectiles, but still. This one was dangerous.

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So here’s the video in all its glory. If you watch closely, he burns a few holes in the screen over the pool. He’ll have a hard time explaining that one to his mom.