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Underwater guns!

Mark SavchukMark Savchuk, A curious Ukrainian
125 upvotes by Frank Heile (PhD in Physics from Stanford University), Can Holyavkin (Molecular Biology and Genetics PhD at Istanbul ... (more) ), Mills Baker, Quora User, Jeff Kesselman, (more)
Hello our dear readers, I have some kick-ass science stuff for you today.

I wanted to write about something exotic and fun. You may know that the new Call of Duty is about to be released (if you don't its ok - not all population of Quora are kids like me).

And there is a very cool scene in the demo where you need to fight underwater. And that got me really curious... How do those guns work?

It all started with a pistol actually. Because the divers in the second world war did encounter enemy divers during the missions. But their conventional weapons were completely useless in water, so the only thing that worked were.... knives.

After WW2, it became apparent that a new weapon was needed. Something more advanced than fighting on knives in a substance 800 times denser than air, so those scary russians made СПП-1М
that could fire bullets up to 11 meters at depth 20 meters but it only had 4 bullets.

It did the trick for a while but honestly speaking it was quite inefficient. So engineers went back to the drawing board to make an underwater gun that had more bullets and longer range. And they came up with APS. An AK-74 rifle converted so it could shoot underwater:
As you can see the first change is the bullet:
needle like bullet with a blunt tip. The reason for it was that it made a cavity around the bullet when it was traveling through water, so it made the bullet much more stable (see the white line?)
Btw - notice the diver's oxygen supply. It doesn't have bubbles. In fact the oxygen cycle is CLOSED. You might think "Aha - its because bubbles make divers more visible, so thats to make them more stealthy." Actually... not really:) Being less visible is indeed important, but the other thing is a closed system provides a much longer oxygen supply. Why? Because the diver has to physically push the air with his lungs INTO the system that uses special filters that take out CO2 from the used air, and put it back in the system for the diver to breath again.

I had a friend who had been serving as a diver in the Navy and he said that it was incredibly difficult on the divers, because if you have to swim fast and you have to work your lungs like crazy to push the air, your head is getting dizzy and they had many occasions when divers simply fainted.... underwater... because they couldn't keep on pushing the air AND performing psychical tasks at the same time.

I bet you didn't know that!:)

Getting back to the bullets - the needle shape made them go straight when fired and the cavity formed around them due to the shape of a tip allowed them go further.

At 5 meters depth the bullet is effective up to 30 meters (range), 20 meters depth - 20 meters, 40 meters depth - 10 meters.

Basically the rule of thumb was - if the diver could see the target he could kill the target.

Another cool thing about the weapon is that it used the gasses (from firing a bullet) to push the bullet into a pocket of air right in front of a barrel, so ONLY the tip ever touched the water.
The weapon had to be designed so it could fire in the air as well, and it did, but it was only effective up to a 100 meters, because the barrel was smooth and not rifled (rifling barrel would cause unnecessary loss of speed when shooting underwater).

The truth was that soldiers used to take 2 rifles - a conventional AK-74 and an APS rifle, which was very inconvenient.

Today Russian navy special forces use АДС rifle
I can go into specs, but basically it does the same thing only better. It can fire in the water AND in the air very well, the range is increased, the accuracy is better and it has an optional grenade launcher under the barrel.

Now for those who DIDN'T watch the call of duty video, go watch it and then continue reading the post......

Ok, you MUST be wondering - Really? The subs make THAT noise? That can kill people?"

The answer is YES (I am just tooo OCD NOT to notice that:) I have noticed the sound waves, I was curious and I have read about it:)

Yes in fact it can kill, not only people, but the subs kill whales and dolphins on regular basis using their sonar devices.

Does Military Sonar Kill Marine Wildlife?
NRDC: Lethal Sounds

"But how does a Sonar make those 235 db sounds?" I hear you say.

Here is how: An electrical impulse from a transmitter (very short bursts of electrical energy generated by the "power pack") is converted into a sound wave by the transducer. That is the wave you saw in the video.

I hope this was fun, I definitely had fun researching that Call of Duty demo:) Those games, huh?:)


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Mark Savchuk
Mark Savchuk
A curious Ukrainian