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MythBusters: Bullets Fired Straight Up

Discussion in 'General Gun Discussions' started by MikeJackmin, Dec 21, 2005.

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  1. MikeJackmin

    MikeJackmin Member

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    Check out this excerpt from a recent interview with the MythBusters guys:

    "We just worked on a myth called "bullets fired up" -- i.e., will a bullet fired directly vertically kill you when it comes back down. We did tons of research on it, and in the end, added significantly to the body of knowledge that's out there on the subject. I won't give away the ending, but we nailed this one."

    All I know about this is what Hatcher wrote back in the 20s. Ought to be interesting...
     
  2. Sry0fcr

    Sry0fcr Member

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    No doubt it can kill or wound you if you're hit. It's happened before.
     
  3. gino

    gino Member

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    Nope, if you fire a gun straight up, it would be like dropping the bullet from a great height. The wind resistance would limit terminal velocity to a speed that would NOT kill you if you were hit by it.


    Sort of like dropping a penney from the top of a tall building. The Mythbusters already did that one and showed that it would not hit hard enough to kill.
     
  4. dolanp

    dolanp Member

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    Not that it matters, the odds of someone being able to point a gun in the precise position to allow the bullet to fall in the same spot are virtually nil.
     
  5. The-Fly

    The-Fly Member

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    i'd beg to differ. When i lived in LA (the city), every july 4th and new years lots of bangers would fire their guns into the air, and usually people would get hit by the bullets returning to ground, wounding and killing them. Think about it, a 100-200 grain bullet coming straight down is going to have a decent terminal velocity, probably several hundred miles per hour, and thats more then enough to penetrate the top of the head. Any engineer or physics majors want to work out the math on what the terminal velocity on a 9mm 147gr or .45 230 grain round would be ?
     
  6. DevLcL

    DevLcL Member

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    Completely wrong. I know a man from pakistan that lost 3 sons all of which died from bullets hitting them in the top of the head going straing down.

    -Dev
     
  7. countertop

    countertop Member

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    This analysis says it won't necessarily kill you but will cause a fairly disabling wound.
     
  8. MrTuffPaws

    MrTuffPaws Member

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    Well after doing some google, I came up with this

    http://www.loadammo.com/Topics/March01.htm

    30ftlbs from a 30cal 150gr bullet can still wound you, and I bet that if it hit right, could kill you and easily kill a small child.
     
  9. rero360

    rero360 Member

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    math isn't my strong point but I would say to fond out the results you determine the max altitude that the round would achieve, I know theres a formula for it but I'm not sure what it is, then you calculate the terminal velocity of the round seeing as how it would indeed be like the round dropping from said height, however I would bet that a bullet would have a higher terminal velocity than a penny due to its hevier weight and its better ballistic coeficient. then you just compare the terminal velocity of the round with the normal velocity and that'll give you a good idea of what the outcome would be. If I had to guess though, from watching various mythbuster episodes where they find the terminal velocity of given objects I would say that for any given bullet your going to be looking at a speed in excess of 100 mph, I'm thinking of about 150, seeing how an average person freefalls at 120mph and a penny is at 60 IIRC so if anyone can fingure it out I'm all ears.
     
  10. Camp David

    Camp David member

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    "Bullets Fired Straight Up" like "arrows fired straight up" leave their point of launch from a specific point on a rotating mass... It is impossible for them to return to that point, simply due to the fact that the mass is moving, 36,000mph... Said another way, the safest place to be after a bullet or arrow is fired "straight up" is exactly under point of launch. Wind, weight of bullet, velocity, and a whole host of other factors will also affect bullet or arrow after launch.
     
  11. Red Tornado

    Red Tornado Member

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    It would depend on the bullet somewhat. A 29gr .22 or a 750gr .50cal at terminal velocity (call it 200 mph, or 300fps from MrTuffPaws source) are going to hit very differently. They'll fall backwards of course, so the bullet type wouldn't matter, as they'll hit base first.

    I'll let someone drop a .22 short bullet on me, if someone will volunteer to stand under the fiddy cal. :evil:
    RT

    Edit: Rero, weight doesn't enter into the equation, just the ballistic coefficient.
     
  12. Cosmoline

    Cosmoline Member

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    So which member of the build team took THAT one for the team, I wonder?

    I always laugh when they put on their bit at the start saying "don't try this at home..." Yeah, I've long planned on building a LIQUID FUEL ROCKET out of PIPES, then testing it INSIDE with a bunch of stored props laying all around it :D They set themselves on fire so we don't have to.
     
  13. poppy

    poppy Member

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    Those guys and gals on MythBusters are pretty good. I watch them all the time especially when they start playing with firearms.

    I'm confident that they will try several bullet weights and velocities and will be pretty scientific about it. I'll wait to see what their results are, but I still will not shoot a gun up in the air, except for a shotgun. poppy
     
  14. HankB

    HankB Member

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    Odds are these were not fired straight up, but at some angle.

    There's going to be a vast difference in terminal effect between something fired straight up and something fired at, say, 45 degrees.
     
  15. Carl N. Brown

    Carl N. Brown Member

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    For a .22 CB Long cap 740 fps with a 30 grain bullet gives me
    about 36 ft/lbs kinetic energy.

    A 150 grain .30 cal falling at 300 fps gives 30 ft/lbs kinetic energy.

    It is NOT enough to be counted on being lethal for the military,
    but I do not want to be under it any more that I would want to
    take a hit from a .22 CB Long!
     
  16. Mad Chemist

    Mad Chemist Member

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    Whether or not the shots are fired straight up or to any angle relative to zenith will make a significant difference in energy retained upon impact.

    If the round is fired straight up(90deg), most of the initial KE is lost. Some kinetic E is converted to potential energy as the object momentarily "floats" at it's apex.
    This leftover energy is bled rapidly during decent from friction.

    A round fired at any angle < or >(but not equal to)90deg will have greater energy upon impact than a round fired at approx. 90deg.

    Physics isn't my strong suit, but this basic idea is correct. IIRC the equation to quantify it isn't very complicated.

    Would any engineers on the board like to take a shot at this.
    Sorry, bad pun.

    JH
     
  17. Czar

    Czar Member

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    terminal velocity is a function of shape. A bullet that is more aerodynamic will have a higher terminal velocity. Imagine a skydiver tucked in a ball vs. spread eagle. They fall faster tucked in a ball since it's less cross sectional area into the airstream, and the shape is more round that flat (2 reasons to fall faster) Same applies to bullets.

    Without conducting any experiments or running any math, lets assume 2 bullets, .45 and 9mm. I bet in this case both would have similar terminal velocities (if they tumble, then FMJ/HP doesn't matter and their aerodynamics are both bad) They fall at the same speed, the .45 will have more energy than the 9mm by exactly the same proportion as it outweighs the 9mm. In this case, I'd rather have a 9mm fall on me.

    neither are going to cause a wound as they would at point blank to 100yards, but let the mythbusters explain away all those killed by bullets returning to earth after celebratory gunfire both here and abroad.
     
  18. MrTuffPaws

    MrTuffPaws Member

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    Weight has nothing to do with terminal velocity because all things fall at the same rate due to gravity, if you ignore air resistance. TV does have to do with shape and cross sectional area though. Pennies are not very aerodynamic so they rotate while falling and they increase their drag. Bullets on the other hand would fall backwards (stability) and have only a cross sectional area that would affect drag. They would have a much higher TV.

    Mass does have effect when it comes to hitting things. More mass, more energy. Either way though, I don't want anything going 200mph to hit me.
     
  19. Carl N. Brown

    Carl N. Brown Member

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    Yes, a bullet fired *straight* up STOPS, zero velocity, then starts
    falling, subject to wind resistence.
    A bullet fired at an angle of 45 degrees or less will retain enough velocity
    to be serious "plunging fire."
     
  20. ScorpioVI

    ScorpioVI Member

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    I grew up in the Southern Philippines (Davao City). By way of celebrating Christmas or New Years it's generally tradition to fire off your firearms into the air at midnight. As a consequence about a dozen people get killed every year from bullets falling out of the sky. One New Year's our house actually took 3 hits from two different calibers.
     
  21. palerider1

    palerider1 member

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    thats just idiotic to fire your gun straight up into the air.
     
  22. trapperjohn

    trapperjohn Member

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    you can not ignore air resistance and talk about terminal velocity. Without air resistance (drag) there is no terminal velocity and a falling object will continue to accelerate untill it hits something. Terminal velocity occurs when the object is falling fast enough that the force of gravity pulling down is the same as the drag force resisting the downward motion.
    now the clinker is that all things being equal a larger body will have a higher terminal velocity. A 10 lb steel sphere will have a higher terminal velocity than a 5 lb steel sphere. thats because as you double the diameter you increase the air resistance by a factor of four, but you increase the weight and therefore the gravitational force by a factor of 8.
    With that in mind a 50 caliber bullet is going to have a much larger terminal velocity than a 22 caliber or even a 30 caliber
     
  23. Carl N. Brown

    Carl N. Brown Member

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    Right, surface area is a square of diameter: volume and weight is a cube.

    Wind resistence is a squared value; weight is a cubed value.

    Bone strength is a square of diameter, while weight is a cube: King Kong
    at 25 feet is three times the size of a big gorilla: his bones are 3 x 3 = 9
    times stronger, but his weight is 3 x 3 x 3 or 27 times heavier, which is
    why he has such a pained expression in most of the movie.

    Drifted totally off subject. Where was I?
     
  24. Mot45acp

    Mot45acp Member

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    Hmmmm

    Would it disable a ZOMBIEEEE:eek:
     
  25. BigFatKen

    BigFatKen Member

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    math

    The world will rotate under you and you will be several feet west of where the bullet will fall. Then there is an effect (like Corliolis) that causes the bullet to move depending on the hemisphere also. it is used in long range artillery placement.

    I'm still not going to try it. Most of the people who reported deaths were from lower angle shots.
     
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