spaceSpace and Physics

Slow Motion Video: Underwater Bullet

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Lisa Winter

Guest Author

941 Slow Motion Video: Underwater Bullet
The Slow Mo Guys

The Slow Mo Guys have a YouTube channel full of amazing videos of ordinary things getting featured (as the name implies) in slow motion, such as a series of mouse traps going off, paint bouncing around on a speaker, deploying an air bag, and many more. 

One of the most fascinating in the collection is a video about shooting a pistol underwater and slowing it down to 1000 times slower than real life.


Wait—they shot a gun underwater? A gun needs a small explosion to fire a bullet, so how can that happen underwater? The gunpowder is contained within the bullet cartridge (unless you have flintlock musket) which shields it from the water and keeps it dry. When the trigger is pulled, the firing pin or striker (depending on the firearm) hits the primer, ignites the propellant, and out it goes. As long as the bullet casing is in tact, it’s no problem shooting underwater. But really, getting your gun wet on purpose is terrible for maintenance.

After the bullet is discharged, the water is forced out of the way. This momentum from the water allows the gas released by the propellent to expand outward more than it typically would. Once the gas is cooled and the water’s momentum slows, the water pressure squeezes the bubble down.

The water resistance slows the bullet dramatically, so it will only travel a few feet. However, please don’t use this information to justify hopping in your pool and trying this out for yourself, as death, injury, and damage to property can occur. Please use firearms responsibly.

Go full screen for this one. It’s pretty badass.



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