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Episode 34: Bulletproof Water, 360 Swing

  • Water stops bullets: confirmed
  • You can do a full 360 on a swingset: mythbusted

The surprising thing about the bulletproof water was how poorly the high-powered rifles did. The full metal jacket bullets for the high-powered rifles came apart upon hitting the water. Even the dreaded .50 caliber rifle was only able to penetrate about 3 ft of water.

I didn't think the 360 swing set myth was that interesting, but if you were patient through the whole episode you got to see them strap rockets on to a dummy in a swing set -- rockets are always good fun on the show. According to host Adam Savage, "Well hopefully that's our job, to strap rockets onto everything"

Bulletproof Water

Myth: Water will protect you from being shot by bullets

They know that water will eventually stop a bullet, so they want to test to see how deep you have to dive to avoid being shot.

Gun selection

The various guns they tested during the myth were:

  • 9mm pistol
  • M1 Garand/.30-06
  • Replica Civil War black powder rifle
  • Shotgun
  • .50 cal rifle

Regarding the .50 cal ammunition:

Adam: "That's what this thing fires?"
Jamie: "It's smaller than my head, it's alright"

Water tank tests

They built a 'ballistic tank' out of 1" thick acrylic and iron girders. They stuck a block of ballistics gel into the tank that could be raised up and down to different depths.

  • 9mm @ 6ft: the bullet went straight through the ballistic gel -- fatal
  • 9mm @ 7ft: the bullet went straight through again -- fatal
  • 9mm @ 8ft: the bullet only went 1/2" into the gel -- non-fatal
  • 3" deer slug + Shotgun @ 6ft: As one might have expected, firing a shotgun into a narrow tank of water shattered the tank and sent everyone running to turn off all the lights to prevent short circuits. The slug shot went through the ballistics gel -- fatal

The shotgun test was the end of that particular test setup.

Pool tests

A vertical rig was a worst-case scenario. In order to make it easier to test and also to make it correspond better with a real-world scenario, they decided to make their new rig be at a 30 degree angle. At a 30 degree angle with an 8 ft penetrating bullet, you would only have to be 4ft underwater.

Someone strangely agreed to allowing Adam and Jamie to shoot off guns in their pool. Adam made a new 20 ft railway for the ballistics gel target and they mounted it at a 23 degree angle.

For the first test they used a replica Civil War black powder rifle shooting Jamie's homemade bullets at 1000 ft/s.

  • Replica Civil War rifle @ 15 ft: The bullet veered way off target.
  • Replica Civil War rifle@ 5 ft: they couldn't find the bullet and the ballistics gel was still intact -- nonfatal
  • Replica Civil War rifle @ 3 ft: The bullet went through the gel -- fatal. At this distance, though, the gel was only 2 ft underwater because of the angle.

They switched to a .223 rifle, which shoots at 2500 ft/s

  • .223 rifle @ 10 ft: the full metal jacket bullet shattered into tiny bits upon hitting the water -- nonfatal
  • 223 rifle@ 3 ft: once again the bullet broke up. The tip of the bullet was resting on the ballistics gel -- nonfatal (myth confirmed)

The next gun up was the M1, which shoots at 2800 ft/s. In their Bulletproof Glass mythbusting, the M1 was capable of penetrating 2.5" of bulletproof glass.

  • M1@ 10 ft: tiny bullet fragments once again
  • M1@ 2 ft: the bullet only pierced the gel 4", which would be enough to just pierce the skin.

They finally broke out the big gun, the .50 cal with armor-piercing rounds, which are shot at 3000 ft/s.

Adam: "Hopefully we'll be gone before the pool fully drains"

  • .50 cal @ 10 ft: even though the water exploded, the ballistics gel was intact. Water made it all the way up to the ceiling. As it was with the previous guns, the bullet round came apart on impact. It lost all of it's energy within the first 3 ft. You would be safe 14" underwater at a 23 angle from a .50 cal.

confirmed: you can protect yourself from a bullet by diving underwater. If the shooter were directly overhead, you would probably be safe from most guns at 8 ft. At a 30 degree angle, you would only have to be 3 ft underwater to be safe.

360 Swing Set

Myth: If you go fast enough, you can swing all the way around a swing set in a 360 arc

Jamie: "Yet another common everyday item turned deadly"

They placed a scale behind a swing set so they could measure the speed of the swing using a high-speed camera.

Kari under her own strength: Kari was able to make it 11ft high (just over horizontal) with a top speed of 23.5 ft/s

Tory under his own strength: Tory cracked his butt as the swing broke under his weight. Earlier they showed Tory reading the warning label on the swing that said it was for kid's use only. Tory didn't make it as high as Kari and only went 22.4 ft/s

Grant in the red safety suit, pushed by Tory and Kari: Tory and Kari were able to get Grant up to 22.9 ft/s and 11.5 ft high

Simulaid Susie (65 lbs) with half-length chain: They shortened to chain to make it easier to flip her over. Grant and Tory tried to flip her over using ropes to pull Susie but were unsuccessful. Tory called in some biker friends and all four of them pulling were able to get Susie over. Even though they got Susie over the bar, it wasn't a full 360 -- closer to 300 before she came crashing down.

The Circus Tests

They did a scale model test with swing set and found that you needed to go 36 ft/s to make it over in a 360. However, if you used a rigid-arm swing instead, you only needed to go 10 ft/s.

Grant, Kari, and Tory went to Trapeze arts in Oakland, where they have a full-size rigid arm swing. Eric Braun, circus acrobat, helped each of them try out the rigid arm swing. One by one they got on the swing and Eric jumped on behind to get it going higher:

  • Eric + Grant: Eric and Grant got up to 230 degrees before Grant asked for him to stop, lest he hurl.
  • Eric + Kari: Eric and Kari up to 240 degrees before she asked for him to stop.
  • Eric + Tory: Eric and Tory made it to 280 degrees but they just didn't have enough energy to make it over.
  • Eric alone: Eric made it easily around

Rocket Susie Tests

They still wanted to get a 360 degree swing on a non-rigid-arm swing, so they decided that they were going to strap rockets onto the back of Simulaid Susie to get her over the swing. They first did some scale model tests to figure out the best way to mount the rocket onto Susie:

  • horizontal (max velocity): Scale-model Susie was sent tumbling and lost her hand.
  • vertical: Pretty useless in getting Scale-model Susie over the bar
  • 40 degrees: Scale-model was sent over the bar four times

With their scale model tests done, they got the full-size Simulaid Susie setup for a real attempt at doing a 360 on a swing set. Despite the results of their scale model tests, they decide to attach four rockets to Simulaid Susie for the actual test for 400lbs of thrust.

First firing: Only one side of the rockets ignited, sending Susie into a spin

They decided to take two of the rockets off so that less could go wrong

Second firing: One side fired off before the other, sending Susie bouncing around and twisting.

They dropped down to a single rocket so that they wouldn't have to worry about simultaneous ignition. They also set the angle at 60 degrees because they were worried about Susie's weight.

Third firing: Susie barely swung back and forth as the angle of the rocket was too steep

They set the angle back to 40 degrees, which meant that they were finally back at the original parameters their scale model said they should have used.

Fourth firing: Simulaid Susie made it over in a full 360



where did they get that 50 cal from again ? I know it was in california. I was looking for a picture of it .

Did anyone else notice something... Totally off by the end results of the water and gun testing? The first half with the straight up and down case I anticipated every move from the guns all going straight through and the shotgun blowing out the sides of the case very easily but as soon as they moved to the pool setting nothing seemed quite right. I don't see how any of that powerful ammo made to not blow to pieces just fell apart in some pool water. Anyone else think there was purposeful sabotage just to end the segment without any further problems?

Breaking the surace tension of the water at an angle, I would expect, is very strenuous to a projectile. It looks to me like the extreme speeds of the rifle rounds were the very cause of the lack of ability to penetrate far through water. The speeds caused a catastrophic failure in the structure of the metals. The metal itself can only handle so much force before it shatters and is destroyed. Hitting water at 2500 fps+ certainly is beyond that point. Notice how high the water shot up when hit.

hey guys

Swing on episode 34: IT WORKS!!! see uups - die pannenshow on german TV!!!

myth busted busted. you actually can do a 360 on a swing. my father did it when i was about 10.

Shooting guns into water is about as common as shooting B. gel. I have shot .270 and .223 into water and the bullets are fine. Other guns tested, .303 and .22 and .22 long. You get some mushrooming but thats it.

As for the .50 cal. IIRC armour percing use a brittle core or shell (don't remeber the perice method on .50). But a plain ball shot would not shatter i'm pretty sure. If you are on a angle however the bullets tend to bounce off from most firearms (i have done it) and this tends to produce a flat spot on lead bullets (not full metal jacket).

Either way this testing is minimal and really adds more to myths than debunks them.

Having said that. Penetration of any bullet in water will be very limited no matter what. (supercavitating rounds anyone?)


Nitpick: the Mythbusters team used a M1 Garand, not a M1 Carbine. I just watched the episode to confirm this. The difference is significant in this case, since the carbine uses a less powerful .30 carbine round, while the Garand uses the .30-06 . In this case, actually, the carbine might have performed better than the Garand, since the high-energy rifle bullets all shattered when they hit the water, while the smaller pistol rounds (which are similar to the .30 carbine round) penetrated further underwater.

@lazybratschu: many thanks for catching the error and the explanation of the significance. I've fixed it above. I should've figured as they've used the M1 Garand in other experiments.

New swinging record will be attempted in Saaremaa, an island of Estonia. The length of rigid arms is 7.07, current record is 7.02.

Yeesh. I was cringing while watching this episode. It is entirely possible for bullets to richochet off water surfaces, especially when fired into the water at an angle (i've seen it happen).

I was wondering what (or who!) was on the other side of the far wall beyond the pool...

In Russia even children can do 360 swing. See the prof here:

what about bullets impacting water at greater ranges? penetration may increase due to the lower velocity (so all those films with bullets whizzing through water might not be inaccurate).

When traveling 3000 fps, a rifle bullet shot from a barrel with a 1:12 twist will be spinning at 180,000 rpm.

This is ultracentrifuge angular velocity. The centripetal acceleration is defined as the radius times the square of the angular velocity.

So for a .30 inch diameter bullet, the radius is 0.00381 meters while the angular velocity is 1,130,973 radians per second, giving centripetal acceleration of 4,873,373,782 meters per second squared. This is equivalent to nearly 500 million times gravity.

The soft lead core of the bullet is held together by the high tensile strength of the jacket material.

As soon as the jacket is damaged, the bullet literally explodes under centripetal force.

I have shot .22-250 and .223 into plasic jugs of water and they will come apart in the first two inches of penetration.

The jug will explode under cavitation effect and when reconstructed, you can see an entrance hole, a ring of fine punctures arranged in a donut about 2 inches into the bottle, and no exit hole.

Pretty neat, eh?

Yuri, The circus tests reflect what is depicted on your page. But the typical american swingsets in backyards and parks have chains.

(also, the preview form in this comment area doesn't have the "kwc" prompt so previewing first fails)

Two days after watching the episode with Tory breaking the swing set, I was sitting on mine while waiting for something, and decided to try swinging for the first time in a while. Well, after I was parallel to the ground, the chain went slack and I went almost straight down and the chain snapped. It was exactly how it happened to him, I immediately thought of that, and I couldn't stop laughing. But now my butt hurts really bad.