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I Water speed and bullet penetration

  1. Jun 23, 2017 #1
    This may be an odd question but I am wondering if water speed affects a bullet's ability to penetrate water.

    Pardon my lack of knowledge, but I am aware that low caliber bullets can penetrate water past 3ft (Thank you Mythbusters). However, the tests they completed were all based around a pool full of water not running water, such as a river or dam. If I my understanding is correct, it is the density of water that causes the bullet to slow down, but does water speed affect this as well? Or would adding water speed the equation only effect the accuracy and not so much the speed of the bullet? I would assume that if water speed would indeed assist in slowing a bullet it would have to be a considerable amount of force in order to do so.

    Just to be clear I am a writer who is looking for some clarification for a potential event in a story, so mathematical calculations for my benefit aren't necessary. I would, however, appreciate some details so that the story can be accurate. There's just something fun about writing an interesting scenario that sounds far fetched but that could actually happen. Thank you in advance.
  2. jcsd
  3. Jun 23, 2017 #2
    I think that the speed of water would effect the bullet too.
    Because if the water is stand still and the bullet move the water is move too (from the bullet view).
    So if the water is move so it speed would increase or reduce (from the bullet view) make the friction would increase or reduce make the bullet speed increase or reduce.
    My literature suck :frown:
  4. Jun 23, 2017 #3

    Simon Bridge

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    The bulk flow of the water will knock the bullet off course in the direction of the flow - think of the water as a whole lots of little particles hitting the bullet... if the flow was towards the gunman, Like if he is in a boat on a river and firing upstream from low down, then it could mean that the bullet penetrates less.

    If your gunnman is firing at a target under water there is probably a bigger effect due to refraction.
    Last edited: Jun 25, 2017
  5. Jun 24, 2017 #4
    Wow that is much more easy to understand :oldbiggrin:
  6. Jun 24, 2017 #5


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  7. Jun 24, 2017 #6
    As long as the speed of water is negligible compared to the speed of the bullet, it can be ignored.
    Maybe if you were shooting up against a waterfall, the effect would be noticeable, otherwise likely not.
  8. Jun 25, 2017 #7

    Simon Bridge

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    replace "more easy" with "easier" :D
    it's practise ... I was mostly saying what you said.
  9. Jun 25, 2017 #8
  10. Jun 25, 2017 #9
    Thank you for the replies. I appreciate the comments and explanations. This points me in the right direction. ^^
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