Underwater gun question (from movie)


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Red Dragon
December 27, 2005, 02:27 AM
I was watching Lethal Weapon 4 the other day and at the end Mel Gibson's character shoots Jet Li's character with an AK-47 while underwater. My question is, would a weapon fire a single shot let alone full auto underwater?

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mbs357
December 27, 2005, 02:58 AM
I'm leaning to an AK-47 not being able to do much underwater.
*shrug*

jdberger
December 27, 2005, 03:13 AM
There was a MythBusters a while back that was about shooting guns into water, most of the faster bullets disintigrated.

Of course, that assumes that there is enough oxygen in the case to make the powder burn...

jashobeam
December 27, 2005, 03:20 AM
Before I bought my Glock (14 years ago) I had read that it could be fired under water. The article said that when fired from a depth of about 3' under water, the 9mm bullet would travel about 10' IIRC.

Anyway, one time when I was out backpacking I stuck the pistol under water and fired off a shot. I held it with my left (weak) hand because I was afraid that something might go wrong and blow my fingers off. The gun fired and cycled normally. I had only brought target ammo, no hollow-points. I think that HP's might not be good to fire under water as they could possibly expand while still in the barrel :eek: ! I had not considered this at the time, but am thankful that I hadn't brought any HP's with me, as I probably wouldn't have realized the possible danger.

Can anyone confirm or refute the danger of in-barrel hollow-point expansion? (I don't mean to hijack the thread.)

TheArchDuke
December 27, 2005, 03:47 AM
I saw a movie a while back, I think it was called "Mindhunters". Well whatever it was called, it was starring "LL Cool J" so I should have known what was coming. Anyway, there's one scene where they have a gun fight under water but the bullets only travel about six feet or so and then sink slowly. That doesn't seem very realistic to me. Maybe I'm wrong. Does anyone know how far a bullet would travel under water? I know it's not as far as it does through the air because of drag but bullets seem to be pretty hydrodynamic (is that a word?) and I'm sure they'd go farther than six feet.

buford1
December 27, 2005, 03:50 AM
I was watching Lethal Weapon 4 the other day and at the end Mel Gibson's character shoots Jet Li's character with an AK-47 while underwater. My question is, would a weapon fire a single shot let alone full auto underwater?


Yes a gun will fire underwater. It will not cycle a auto-loading firearm. Gun powder requires no oxygen, as it creates it'a own. I would imagine it could be lethal up to several feet. No damage will happen to the gun because the water pressure inside the barrel is off set by the water pressure on the outside of the barrel. The gun must be fully submerged, to just stick the end of a barrel in water and shoot it is crazy.:eek: :eek:

jdberger
December 27, 2005, 04:02 AM
Gun powder requires no oxygen, as it creates it'a own.
Thanks for the clarification.

VirgilCaine
December 27, 2005, 10:15 AM
I saw a movie a while back, I think it was called "Mindhunters". Well whatever it was called, it was starring "LL Cool J" so I should have known what was coming. Anyway, there's one scene where they have a gun fight under water but the bullets only travel about six feet or so and then sink slowly. That doesn't seem very realistic to me. Maybe I'm wrong. Does anyone know how far a bullet would travel under water? I know it's not as far as it does through the air because of drag but bullets seem to be pretty hydrodynamic (is that a word?) and I'm sure they'd go farther than six feet.

No, that's pretty accurate. Water is pretty good at slowing bullets down. The mythbusters episode showed that faster bullets tore themselves apart IIRC, but slower ones did not. So James Bond should worry about the Makarov sidearms and not the RPDs and AKs when he jumps into the water to escape the nasty Soviets (just an example).

PzGren
December 27, 2005, 11:13 AM
The German Kampfschwimmer, SEALS, use a H&K P11. It is a revolver - type gun with the chambers sealed. They came up with this after some testing so there might be a reason to it.

benEzra
December 27, 2005, 01:25 PM
Some handguns (usually 9mm's) can be fired underwater w/o breaking--the Glock 17 is a famous example--but when you go to longer barrels and higher-pressure cartridges, you are more likely to get a burst chamber/barrel than a discharge. A barrel full of water resists the acceleration of the bullet, sending chamber pressures through the roof, often enough to swell the barrel, burst the chamber, or otherwise break the gun; the longer the barrel, the greater the resistance. A number of people have blown up their Glock .40's trying to replicate the shooting-underwater trick...the .40 runs a higher chamber pressure, and a .40 barrel holds more water than a 9mm barrel.

Now, having said that, the Russians did make an automatic weapon specifically designed to fire underwater (for special forces use), but it fired long metal darts at a relatively low velocity, and these would travel for 100 feet or so in water, IIRC. It bore some resemblance to an AK-47, so it may be that this was the gun used in the movie rather than an AK.

Nick_90
December 27, 2005, 01:28 PM
I would never ever try firing underwater with any gun whatsoever. I know Glocks are sometimes provided with an extra part in order to fire underwater but it remains rather dangerous.
A quick look around the Internet should provide you with enough horror stories to discourage you from trying.
However, IN CASE OF AN EMERGENCY, it is true that you'd better completely fill the barrel with water before shooting underwater. If only half full, you are sure to have a Ka Boom.

Travis McGee
December 27, 2005, 03:58 PM
Don't do this with AR type rifles! Even after being dunked, be careful to retract the bolt and allow the gas tube and barrel to drain. The residue in the gas tube can trap water after submersion, and lead to dangerous results and damaged receivers. Iikewise, water in the barrel can cause catastrophic failure.

KriegHund
December 27, 2005, 04:03 PM
IIRC if you fire a gas-operated weapon that was submerged in water and still has alot of water in it it can create steam that will blow the tubes up??

TechBrute
December 27, 2005, 04:05 PM
Don't do this with AR type rifles! Even after being dunked, be careful to retract the bolt and allow the gas tube and barrel to drain. The residue in the gas tube can trap water after submersion, and lead to dangerous results and damaged receivers. Iikewise, water in the barrel can cause catastrophic failure.
Can you provide your source, please?

Carl N. Brown
December 27, 2005, 04:06 PM
An old Sea Hunt episode had Lloyd Bridges firing a revolver underwater as
a test. 1950s Nostalgia.

About the only thing that works underwater as a credible weapon
are those Russian spearguns, some of which resemble AKs, but
even then the range is limited.

Water resistence is much greater than air resistence on a projectile:
try throwing a rock underwater.

avpro
December 27, 2005, 04:11 PM
On the Myth Busters show, they fired all sorts of calibers at ballistic gel that was 3' under water. None of the bullets reached the gel. They then moved the gel closer (I think 18"). Only one bullet reached the gel. It was a low velocity bullet. All of the .223, 30-06, and even .50BMG could not touch the gel just 18" under water! So if you are being shot at, you will be safe just 18" under water. So all those movies you see like Saving Private Ryan where the bullets where going through the water and then right through some poor guy under water, won't happen. At least according to Myth Busters ;)

mbt2001
December 29, 2005, 01:14 PM
I think that is why they used the AK-47. Ballistics aside, the cycling of the gun was real. That is a tough weapon and NOTORIOUSLY realiable...

I wish we could say the same for the AR-15 / M16 guns...

WvaBill
December 29, 2005, 01:54 PM
Can you provide your source, please?

I remember reading that, but only found this:

A water-filled barrel first must be drained because water can block the barrel and gas tube. Firing produces tremendous pressure that may cause the weapon to explode. Some assume that water will simply blow out of the way, but this is not entirely true. If water is toward the back of the barrel, it can't move out of the way quickly enough, so it acts as an obstruction--similar to dirt, sand or a cleaning rod stuck in the bore. Dirt and sand are hard to remove because they stick to the bore and chamber. Water is much easier to deal with; you don't need to break open the weapon or swab the bore as you do with dirt and sand.

http://www.safetycenter.navy.mil/media/groundwarrior/issues/summer02/twom4s.htm

TechBrute
December 29, 2005, 11:23 PM
Thanks!

shermacman
December 29, 2005, 11:35 PM
It was on a hot day, this past August, when I jumped into the shallow end of our pool. I was wearing my trusty black, tacticle Speedo a Glock 23 in .40 and my S&W .357 wheelie.

The first six rounds were .38 wad cutters. All fired, all traveled about 6 feet and dropped to the pool bottom. The bullets exhibited no expansion. The second six were full party house hand loaded .357 rounds. Same deal, they traveled a couple of feet farther but no more than eight feet total, no expansion.

The Glock fired but would not cycle. Same deal, six feet of travel, drop to the bottom, no expansion.

My head was out of the water, the sound was like a thump, no one in the house heard a thing. I was underwhelmed.

I had better never catch my kids trying some stoopid stunt like that!

ctdonath
December 30, 2005, 04:18 PM
Yes, some guns can function reasonably well underwater.

Any proper discussion comes with extreme warnings of don't try this at home, do it at your own risk. Can be done safely, but mistakes and failure can be extremely serious.

Hollowpoints will expand in the barrel, causing "kabooms" and hand damage.
As water does not compress, sonic impulse is transferred efficiently and can easily destroy eardrums and cause other serious harm.

That said, done right some common firearms can function underwater.

The Glock 17 can do so when fitted with "marine spring cups", filled entirely with water, and loaded with FMJ ball rounds. Effective range is somewhere around 11 yards, able to punch thru plywood. Some divers use 'em against sharks.

The XM8 is designed to function with a barrel full of water.

This thread appears periodically, and is usually full of misinformation. Search the web for pages (there are several) describing how to do it correctly in detail.

TechBrute
December 30, 2005, 04:29 PM
This thread appears periodically, and is usually full of misinformation. Search the web for pages (there are several) describing how to do it correctly in detail.
Thanks for setting us all straight. Can you provide some sources for your information?

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