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Comment by satvikpendem | Hacker News Reader

Related, hitting a Prince Rupert's drop with a bullet: https://youtu.be/F3FkAUbetWU?t=104

TLDW: The bullet shatters and the drop stays intact.

I wonder what the results would be if done with a steel core/AP type rifle round , the bullet in the video appears to be jacketed plain lead at pistol velocities.

The same channel did a follow-up with rifles here: https://www.youtube.com/watch?v=k5MORochIDw

For sure some very different results but it looks like they're using low cost jacketed plain soft lead. I wonder what the results would be with an M855A1 (available to civilians) or real armor penetrating designed round.

https://smallarmssolutions.com/home/the-m855a1

The difference in muzzle energy from a .38 special revolver and a mini-14 (5.56 NATO with an 18.5" barrel) is so high, it's not surprising.

I’m surprised the fragments didn’t cause the whole thing to shatter when they came into contact with the tail

They describe (at 2:19) that they annealed the tail to remove the tension allowing it to stay intact.

So we should make body armor out of Prince Rupert drops?

Body armour dissipates lots of the bullet energy in the act of breaking. Prince Rupert drop armour would mostly result in the bullet snookering a glass chunk into you instead. Even if you could make a solid glass plate that wouldn't break when shot (doubtful), the transmitted energy of a bullet would still be more damaging because it would all end up in your body, not in heating up the broken shards of a ceramic plate.

Disagree. People regularly absorb blows with more energy than a bullet without injury.

For those downvoting this, remember that firing a bullet has exactly the same impact on the hand holding the gun.

The same impulse (force times time), not the same energy.

The transmitted energy does end in your body in case of normal bulletproof vest tho. Only very little is converted into heat, the main job is to spread it around. Movies as usual do a terrible job of portraying reality here.

Ceramics aren't used because they break on impact, they are used because they are harder per kg than steel so the whole thing can be lighter.

Imaginary "unbreakable plate" would still be backed by layers designed to slow down the pulse and dissipate that energy and if it was thinner and lighter than ceramics that means you can put more materials behind it and still come out ahead

Only the head of the Prince Rupert drop is tough, due to high levels of stress in the glass (its made by dripping viscous melted glass into water). Interestingly, the whole drop with shatter into glass dust if the filament like tail is broken!

Wikipedia has a good description of this. [1]

[1] https://en.wikipedia.org/wiki/Prince_Rupert's_drop

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