Monday, August 30, 2010

Firearm Myths and Truths

We looked at some firearm myths last month. Now it is time to examine some more stories and see if they are really myths or true facts.

1. You can escape bullets by diving underwater.

We've all seen the movie scene where the hero swims underwater, while all the villains impotently shoot at the water in an attempt to hit him, but our hero emerges unscathed on the other end. Is this really possible, the reader asks. Well, there is a fair bit of truth to this. We've all seen people shooting into bottles filled with water and puncturing them with splashing all around. However, it is a different matter when one shoots into a larger body of water, such as a lake. Water offers a lot of resistance to bullet movement and slows down bullets considerably.

The popular TV show Mythbusters ran an episode where they tried to confirm or disprove this story. They rigged up a block of ballistic gel to simulate a human body and immersed it in a public swimming pool and then shot it with various weapons. One of the interesting things they noted was that slower moving snubnose bullets from a 9mm pistol seemed to penetrate deeper into the pool than faster moving spitzer bullets from rifles like the M1 Garand. In fact, faster moving spitzer bullets tumbled when they hit the water surface and quickly lost their speed. At certain angles, the bullets just disintegrated upon hitting the water surface.

They initially tried shooting a 9mm pistol vertically into a plastic acrylic tank containing water and a ballistic gel block and noted that the bullets lost enough speed that it couldn't penetrate the gel block below 8 feet (2.44 meters) of water when fired directly vertically in (which is the worst-case scenario). They then shifted operations into a bigger body of water, i.e. a local swimming pool.

In order to make things more realistic, they conducted the swimming pool tests by shooting at a 30 degree angle into the water surface (just as the guards might shoot at the hero escaping from the wall of the castle) and they discovered some surprising results:
  1. Using a replica civil war rifle, they couldn't hit the block of ballistic gel from 15 feet (4.57 meters) or even 5 feet (1.52 meters) distance because the bullets kept swerving off in the water. When hitting it from a totally unrealistic 3 foot (0.91 meters) range, they managed to get a fatal penetration. Bear in mind that the gel was in only 2 feet (0.61 meters) of water for this to happen.
  2. Using a modern day assault rifle shooting NATO 5.56x45 mm. ammunition, they tried shooting at the gel block from various ranges. Bear in mind that this weapon fires a bullet at 2500 feet/second (762 meters/second), which is way faster than a civil war era weapon. At 10 foot (3.05 meters) range, the jacketed bullet just shattered when it hit the water surface, with no fragments in the gel block. At 3 foot (0.91 meters) range, the bullet broke up as before, but the tip of the bullet just slightly penetrated the gel block in what would be a non-fatal injury.
  3. Using an early 20th century M1 Garand rifle (which fires a bullet at 2800 feet/second (853 meters/second)) showed similar results. At 10 foot (3.05 meters) range, the bullet simply shattered on hitting the water surface and at 2 foot (0.61 meters) range, it barely penetrated the gel block.
  4. They used a huge Barret 50 caliber rifle capable of shooting at over 3000 feet/second (914 meters/second). Bear in mind that this is a sniper rifle capable of long range shooting. Result: The bullets created a big splash upon hitting the water surface, but either disintegrated or lost enough momentum after travelling in 3 feet (0.91 meters) of water that they couldn't inflict a fatal wound to anyone below this depth.
Conclusion: This scenario could actually work if the person is deep enough under water, as water does decelerate bullets by a surprisingly huge amount. Also, faster moving spitzer bullets tend to disintegrate a lot quicker when they hit the water surface, depending on the angle and speed they're fired at.

2. You can fire a gun underwater.

Some readers may have heard of special forces using guns that can fire underwater and such. For instance, there is the Russian SPP-1 pistol invented for combat divers. The actual truth is that you don't need a special gun that fires underwater, because most modern ordinary weapons can also do so, but doing this is an extremely bad idea.

The first problem is that sound carries a lot further underwater, so if a person happens to be underwater when firing a weapon, it could rupture their eardrums and severely disorient them or even knock them out with the shockwave.

The second problem is if the barrel contains an air bubble when underwater, the bullet travels through it and then hits water. Since water isn't as compressible as air, the pressure spreads in all directions. At this point, with all the pressure building up, something has to give and usually it ends up with either the barrel or the action exploding.

The reason some people think that guns can't fire underwater is because black powder won't ignite when wet. Well, most modern weapons don't use black powder for their propellant. They use cartridges filled with modern propellants, which are capable of burning even when underwater.

So what happens if you clear the weapon of all air bubbles and then attach a thread so that the weapon fires underwater while the user stays out of the water (or at least with their head out). In this case, most modern weapons, such as a Glock or a SiG 9mm pistol will fire, as will rifles like an M-16 or a Garand M-1. However, the range of the weapon will be severely shortened because water tends to offer significantly more resistance to bullet movement, a fact that we already noted in our last section. A test by the Mythbusters TV show determined that an M-1 Garand bullet only had a range of around 6 feet (or less than 2 meters) when fired underwater. Also, the resistance of water also applies to the operating mechanisms of automatic and semi-automatic weapons. This means that these weapons will most likely not go through their operating cycles and hence will only fire one shot.

Conclusion: Yes it is possible, but it is an extremely bad idea.

3. You can come out of the water and start shooting immediately.

We've all seen scenes from Rambo movies where Sylvester Stallone's character suddenly pops out of the river and starts shooting people around him. So what's the truth here?

Like we noted in the previous section, water is not a very compressible fluid, so it is a good idea to get as much of it out of the barrel as possible before firing. If not, when the bullet hits the water pocket, it will try to push it out of the way and the water not being compressible is pushed with high pressure to the sides of the barrel. The barrel is usually not built to handle these levels of stress and may possibly explode. So, obviously, the key is to do one of two things:
  1. Empty the barrel and action of as much water as possible very quickly, so it is possible to shoot the weapon. This means the barrel must have strategically placed drain holes to do this.
  2. Make the barrel much thicker to handle higher pressures. However, this increases the weight of the weapon.
Both these methods are used by various manufacturers of modern Special Forces weapons. Examples of these would be Heckler & Koch HK-416, Magpul ACR, Robinson Armament XCR etc. In fact, there are videos of what is called the "Over the Beach" test that some manufacturers advertise, to show how quickly their weapons can be pulled out of the water and fired.

But recall that Vietnam Era special forces did the same thing with regular M-16s as well. So what did they really do? Well, the reality is that they had to clean their weapons and drain them out before using them. On leaving the water, they would point the barrel downwards and then pull back on the forward assist lever to break the tight seal in the barrel. This would allow most of the water to drain out. In fact, one of the early objections in the M-16s design was that the barrel was of 5.56 mm. diameter which meant more water would stay in the barrel due to capillary action, whereas a wider barrel would drain it quicker. That is why the field manual recommends against carrying the barrel upwards in heavy rain, otherwise water could get stuck in the barrel. The interested reader is welcome to read a now declassified report about the issues of the AR-15 (the prototype M-16) here: For those interested in how the procedure of draining water from the barrel of an M-16, chapter 2, page 0009 00-7 to page 0009 00-10 ("Unusual operating conditions") of the Army manual TM 9-1005-319-10 describes how it is done, along with pictures.

The new M16 Mark 4 Mod 0 has modifications to drain water from a barrel in around 8 seconds. This means it can start firing a lot quicker than its predecessors, but the user still needs to wait for water to drain first before firing. That means Hollywood is generally gassing when it shows people shooting the moment they come out of water.

There is also a secondary big movie myth here. Recall that the hero usually comes out of a muddy river and starts shooting immediately. Now a muddy river contains water, but also contains mud, silt, dead leaves, tiny fish, sticks etc., none of which is a good idea to have in a barrel when the shooting starts. In fact, it is a good idea to have nothing but air in the barrel before shooting. In Vietnam, special forces personnel would come out of the water and hide in a quiet place while they spent some time getting all the mud out of their weapons.

So what does a user who carries his weapon in the heavy rain do if he wishes to shoot immediately. First, one option as stated by training manuals, is to carry the weapon barrel downwards, so that rain water and other debris don't enter the barrel. Another option is to apply a condom at the end of the barrel. This keeps the water out and it is easily torn away by the first bullet coming through the barrel and doesn't affect its flight path that much either. In fact, there is a commercial product called a "barrel cot" that does exactly this and it is often used by hunters who hunt in snow or muddy conditions.

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