Mythbusters go shooting again!

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jtward01

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The guys on Mythbusters decided to find out whether swimming under water would protect you from gunfire. They tested a 9mm pistol, a 12 gauge shotgun, an AR-15, a .30 cal. M1 Garand and a .50 BMG rifle.

The started out with a 10-foot-high water tank in which they lowered a block of ballistic gelatin. The 9mm penetrated the gel completely down to seven feet but at eight feet it barely penetrated the front of the gel block. Then they tried the shotgun. The pressure from the shotgun blast blew out the sides of the tank and the shockwave alone was enough to blow a cavity out of the back of the gel block, however the pellets did very little damage. Chances are, in open water the shotgun would not be very effective.

They moved to a swimming pool to test the AR, M1 and .50BMG. In all three cases the bullets disintegrated before striking the gel, which was only about 14 inches below the surface, but at a slant line distance of about 10 feet from the shooter. So, when shooting at a subject swimming underwater a 9mm pistol is much more likely to cause a serious or fatal wound than even a .50BMG.
 
Gotta love those guys. I know I couldn't find anyone willing to let me use their swimming pool for a test like that!

I'm a bit surprised about .223 not doing better, perhaps its the infamous "tumble" effect?

If 9mm did well, then would .357SIG (or .357magnum) do even better? Or is higher velocity working against water penetration? I don't know much about the physics of it.
 
Were they also shooting 9mm from 10ft away at slant angle? I can't imagine rifle rounds not do as well as pistol.
 
Higher Velocity = Less Penetration

The magnitude of the force being applied to the nose of the bullet follows the square of the velocity.

I.E. If you double the speed the force quadruples, and if the speed triples the force is 9x greater.


With the higher velocity rifle bullets the force on the nose of the bullet is so high that it causes the bullet to deform so far and so fast that it basically desintegrates. The tiny pieces that result lose their velicity very very fast.

With the pistol bullets and whatnot, the velocity is low enough that the resulting force isn't enough to majorly deform the bullet. Thus it just "coasts to a stop", so to speak.
 
I loved Adam saying "Oh boy, another myth where we get to shoot guns!"

Even though Jamie did all the shooting.
 
Higher Velocity = Less Penetration

Hrm. So something like a .45-70 should be the best swimming pool penetrator? :)

jmm
 
Old stock tank, a .40 S&W and a .223

A while back, a buddy of mine who swears by his .40 came by my folks place to visit and shoot. Dad had a plastic stock tank that cracked near the bottom and was about to be hauled off to the great junk pile in the sky when Dale and I decided to shoot at it.

His .40 would get about three quarters of the way across the tank, then stop. Made a plume of water about three feet high on impact.

My .223 would get about half way, at least that's where we found the jackets, never found a core. Shot water about ten feet into the air on impact.
 
There was a thread on this one not too long ago and someone had the video for download. Try a search - hopefully it will still be there.
 
Hrm. So something like a .45-70 should be the best swimming pool penetrator?
Click to expand...
You probably want something a little more aer... hydrodynamical. I am guessing a long, thin bullet is better than a short, fat bullet.

I know that a low velocity (subsonic) bullet travels further in water than a high velocity bullet of the same shape and caliber. I tested that as a teenager, 20 years before the Mythbusters... :)
 
I saw this episode a while back...

The best penetration under water was from an 1853 Enfield .577" rifle musket.

The high velocity, spitzer bullets from the AR, M1 and .50 cal. whould just tumbel and shatter as soon as they hit the water.
 
I like at the end where he holds up the frags of the .50 round and calls it AP even though it is clearly a regular fmj.
 
The shotgun they used wasn't firing pellets, they fired a deer slug penetration was impressive as was the blowout wound to the gel.

Slow (subsonic) bullets penetrate a lot farther than hypersonic ones.
 
The 9mm and shotgun results may be an anomaly, as those two were fired at a 90 degree angle into the water, and the rest were fired at a fairly shallow angle - 23 degrees, I think I saw somewhere.

I'd really have liked them to re-do the 9mm and shottie at the shallow angle after they broke their water column in the shop.
 
It would seem to follow that like the .577 smoothbore musket, the shotgun is a slow and heavy round.

The point at which fragmentation vs. penetration occurs would be interesting.
 
*counts the time in seconds for how long it will take for the conversation to switch to Kari...*
 
grimjaw said:
Higher Velocity = Less Penetration

Hrm. So something like a .45-70 should be the best swimming pool penetrator? :)

jmm
Click to expand...

Judging from the fact that the shotgun slug shot clean through and utterly destroyed their 10' high water tank, yes I'd say the .45-70's big slow bullets would plow through water like torpedoes.

Sectional density, of course, plays a critical role in penetration. I would be very interested to see how far a RN solid 7mm in the 170 grain range at aboud 2,100 fps would go through that pool. My guess is it would poke a hole in the bottom.
 
No wonder they don't let Adam shoot a gun. Funny guy, but bad trigger discipline. During the opening sequence, he has his finger on the trigger of a large revolver and I think he sweeps Jamie!

Jamie is always very careful with firearms.
 
nfl1990 said:
I like at the end where he holds up the frags of the .50 round and calls it AP even though it is clearly a regular fmj.
Click to expand...

I actually don't know if I would fault him for that. .50BMG FMJ probably goes through a lot of steel, even if it's not AP. That's a lot of lb*ft!
 
TMM (No Relation) sez, "*counts the time in seconds for how long it will take for the conversation to switch to Kari...*"

Not in this forum, we're all too serious, but if I was a youngster, single in my 30s with 10 - 11 Million in net worth, and I could handle a VEGITARIAN, who can handle a Submachine Gun, I might try for an introduction.

Geoff
Who notes Jamie is the BOSS, everyone else is just glad he found a way to keep them gainfully employed when business was slack. :cool:
 
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