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Mach 3

  1. Jan 23, 2004 #1
    If a bullet exits a barrel at 3000fps. Does the breaking of the sound barrier by the bullet influence the BOOM that you hear.
    Thank you.
     
  2. jcsd
  3. Jan 23, 2004 #2

    LURCH

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    Yes, it adds to the volume and intruduces a slightly different tembre. Have you ever wondered why sniper rifles are not silenced? After all, if the idea is to remain hidden, silence would seem like a good thing, no?

    But a silencer would do no good on a weapon that has a supersonic muzzle velocity, besause the bullet coming out of the barrell and striking the air makes a sound very much like a gunshot.
     
  4. Jan 23, 2004 #3

    Njorl

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    Actually, there are some silenced sniper rifles, but they use subsonic rounds. They are very interesting. They make up for some of the lost accuracy by imparting much more spin to the round.

    Njorl
     
  5. Jan 23, 2004 #4
    Thank you, you two.:smile:
     
  6. Jan 23, 2004 #5

    russ_watters

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    But only some - it greatly increases errors due to things like wind and geometry (distance, height, etc). Firing a sniper rifle isn't actually all that much different than firing an artillery shell.
     
  7. Jan 23, 2004 #6

    LURCH

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    I have heard of such rifles, now that you mention it. Can you recall the name of one? I'd like to snoop around and find some data on them. I think one of the reasons they are not-so-popular might be range. After all, added rifling might make them somewhat more accurate [than they would be without] up to a certain distance, but lower muzzle velocity must meen shorter range.
     
  8. Jan 24, 2004 #7
    The VSS Vintorez is one such rifle that uses subsonic rounds.
     
  9. Jan 25, 2004 #8
    Does anyone know of some more general information on speeds, wind effects, etc, that go into sniping? It has always interested me (in a physics sort of way, of course).
     
  10. Jan 25, 2004 #9
  11. Jan 25, 2004 #10
    Subsonic rounds are silenced, but they come at great reduction of stopping power. I think range is reduced as well, not entirely sure on that. I believe the VSS Vintorez fires a 9mm(?) round - rather unusual for sniping, considering that most sniper rifles use 7.92mm design. I guess to make up for that disadvantage the sniper would probably use hollow-point rounds when sniping soft targets.

    I wouldn't see the advantage of using subsonic full metal jacketed rounds unless the sniper plans on targeting someone with kevlar armor.
     
  12. Jan 26, 2004 #11
    i read this thread and happy because i have always wondered why they havent been silenced in movies and wat not, so anyway in my hype i told a friend of mine who was a gun collector. He told me that the record held for the greatest distance a sniper rifle can fire was 2.6 km, this was held by a subsonic rifle. hmm? Any one wanna comment?
     
  13. Jan 26, 2004 #12

    russ_watters

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    Doesn't make a lot of sense that a subsonic would fire further than a supersonic round.

    And they never do the sound right in movies anyway - a semi-auto pistol still makes a pretty loud "click" when the action moves.
     
  14. Jan 26, 2004 #13
    I do alot of shooting. Thats why i posted the question. I was always curious about it. Anyways. Snipers are usually shooting very long distances so they need the velocity. Even at the range shooting at a steel gong 400 yrds away. You squeeze the trigger, you can see the gong move and a dust patch behind it,then after what seems an eternity you hear the bullet hit the gong. You can actually move out of position before you hear it hit. Thats why snipers work in 2s i think. You have a shooter and a spotter in 2 different locations. The shooter can change positions before the people at the other end even hear the blast. The spotter confirms the kill.
     
  15. Jan 27, 2004 #14

    Njorl

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    For those who are interested in the world of snipers, I highly recommend Stephen Hunter's novels, particularly the "Bob the Nailer" ones. The scene from "Time to Hunt" where a sniper team slows down a full infantry division is very memorable.

    He also has one about the development of a subsonic sniper rifle. They used a pure lead, unjacketed round. It expanded when fired, filling the bore more completely. It gave up linear acceleration for angular acceleration.

    Njorl
     
  16. Jan 30, 2004 #15

    LURCH

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    Interesting trivia regarding snipers;

    Noted expert on human sexuality Dr Ruth Westheimer has Israeli citizenship, which meant she had to serve in the armed forces. When she reported for duty, the Israeli military took one look at her diminutive size and decided she would be easy to conceal, so they made her a sniper.

    So the next time you see this cute little granny/munchkin looking "sweet little old lady", remind yourself that she could put a bullet through your eye at 200 yards![b(]

    (I wonder if she would do that squeeky little laugh afterwards?)
     
  17. Jan 30, 2004 #16
    Do you think body armours would do the work protecting u if someone snipes you from lets say, 1/2 miles distance? They are designed for it right?
     
  18. Jan 30, 2004 #17

    russ_watters

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    Body armor is designed for specific impact energies, so it depends on the gun/bullet. A .50 cal high velocity bullet at 1/2 mile would barely even notice a kevlar vest and would go through your body like it wasn't even there.
     
  19. Jan 30, 2004 #18
    ok thank you:smile:
     
  20. Jan 30, 2004 #19

    Njorl

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    Now, now boys. I'm going to be reading the papers. If I hear about anybody in body armor getting sniped with a subsonic rifle, I'm gonna forward this to the FBI.

    Njorl
     
  21. Jan 30, 2004 #20
    No need, Njorl. As soon as the word 'sniper' appeared in the first post, all succeeding posts were automatically downloaded onto the NSA hard drive for easy access by 'authorized' personnel on a 'need to know' basis, along with each posters real name, address, social security #'s, and ...ummm, mother's maiden names, girl friends phone #'s..., dental records,...and a few other pieces of positive I.D. paraphenailia.


    ____________________________________________________________________
    Just because you know you're paranoid doesn't mean someone is not out to get you.
     
    Last edited: Jan 30, 2004
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