mythbusters!!

Did anybody see Mythbusters tonight on discovery channel?

If not you missed it

Episode 34: Bulletproof Water How deep must you dive to survive a gunshot? Adam and Jamie are on the case, unleashing their arsenal of pistols, shotguns and supersonic rifles to find the answer.

You know the old saying that if someone is shooting at you then you run and jump in a lake and they will have a less likely chance of hitting you. They put it to the test tonigt
They came up with an interesting answer. Suprisingly enough you can escape gunfire by diving underwater But how deep and what calibers is the question.

Even the largest weapon they had which fired the .50 broke to pieces upon penetration of the water. Great show. Must watch it if you get a chance. Trying to find more info on it

With the angle of the target and the depth of the water calculations, for most rounds it came out to something like 10 inches to 2 feet of water would be enough to protect you. At 10 inches, you would get 4 inches of penetration from an M-1 Garand. At 2 feet with a 23 degree angle on the target a civil war muzzle loader would penetrate with enough force to kill, but at 5 feet the round would curve so much they had trouble even FINDING it. The .223, M-1, and Barret all shattered on impact and fell to the bottom in itty bitty pieces.

so I take it you have seen it. It was a really good show. At least i thought so. 1 question though. Why did the bullet break up into numerous pieces upon penetration of the water? Was it due to the heat of the bullet mixing with the water which cooled the bullet down so quick it shattered. Any one know why. I don't remember them stating a reason

It was a combination of factors. When the bullet hits the water, it's travelling at supersonic speeds. At the time of impact, it almost immediately decelerates to subsonic. I believe that combined with the heating/cooling factor are what causes it to shatter. I believe it's mostly the deceleration though.

How about letting the guys from Mythbusters examen the collapse of the WTC... See what they come up with....

Wow that's interesting. I've always wondered that, but I don't think we get mythbusters here.

I was rather surprised when I saw the results. I expected a lot of deflection, and them having a hard time hitting the target, I didn't expect them to just shatter like they did. And they shattered into a lot of very small pieces. They had the camera on the target, and after you heard the shot, you just saw the small black specks floating towards the bottom. I was expecting something more like the muzzle loader, where it hit the water, and curved in all sorts of directions.

DAMN IT! I simply must get Sky.

Very good topic and kinda blows Hollywood out the water (excuse the pun)
where the bad guys die in a hail of lead.

A sudden thought, how long do you have to hold yer breath?

Im not surprised at all by the results. A muzzle loader has relatively low muzzle speed. Since modern rifles have at least twice the muzzle speed, their impact energy is more than 4 times higher. and the faster one hits water surface, the "harder" the water will be. Its like a sturdy beer glass, if you drop it from 1 meter it will probably bounce off the ground and stay intact, if you drop it from 2 meters it will most likely shatter.

Apart from that, many modern bullet types are SUPPOSED to shatter, which increases the effect, although I dont know which ammuntion was used in the tests.

Maybe new armors should have a water layer

Originally posted by skippytjc
Maybe new armors should have a water layer

Not water but a viscous crystalline material that behaves like liquid glass.

www.military.com...

Called 'Sheer Thickening Fluid' it has roughly the consistency of honey when stirred gently, but it's very fluid behavior transfers impact shock more efficiently so that the PEG chains form giant molecular monocrystals of surprising strength when suddenly subject to accelerative inertia.

In terms of water, I am a bit surprised, as I know of multiple instances of HMG rounds being used for below waterline kills on both assault landing craft and in one case (Wake) to sink a IJN destroyer performing offshore gunfire support to landing Japanese troops.

At the same time, water is _utterly incompressible_ under nearly any natural force you care to apply to it.

So that if you formed a large enough impact shock in front of the round (so that the H20 could not displace rapidly enough) the effective phase change to a pseudo-solid would be instantaneous. At which point (depending on round shape and grazing angle at impact) the bullet would most like and likely tumble and then break up as the density variations between the outer brass or steel jacket and the inner lead or tungsten/ceramic cores would cause incredible mass differentialed decelerative behaviors that would like result in frangilate behavior on the projectile as a whole.

That said, it should also be noted that there ARE guns which work, quite effectively, underwater. Any of the 9mm Glocks with a fluted firing pin and seal discs works well enough, (with FMJ rounds), though range is low.

And the Russians came up with a 'needle gun' that uses a flat head to generate a supercavitating bubble around the front end of the long, skinny, projectile.

world.guns.ru...

So it's basically all about sectional density and the ability to sustain smooth displacement around the projectile that keeps the fluid laws working for you.


KPl.

Perhaps a .50 Cal from a barrett, but I doubt you would be safe from a .50 MG being constantly fired, not only are these bullets not travelling as fast, but also are coated with metals like copper or brass.

I doubt steel bullets would shatter either.

They used standard FMJ rounds that you'd buy from any gun store. I wasn't surprised so much that the muzzle loader didn't shatter. I figured that one would just curve.

There was a suggestion a while back for bolt-on vehicle armour that consisted essentially of water-filled panels working on this principle. Not sure how well it would work in practice, but mythbusters suggests it would do some good.

The RAMICS 30mm mine-destroying supercavitating round can apparently go through some tens of metres of water and maintain enough KE to destroy a mine; during WWII the US Navy had collared projectiles which achieved the same sort of effect for below-waterline hits.