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CSI and bullet trajectories

Discussion in 'General Gun Discussions' started by Snowdog, Aug 10, 2005.

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  1. Snowdog

    Snowdog Member

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    After seeing an older episode of CSI, a program I recently became interested in, I saw a "recreation/illustration" of how a lady was struck down by a 9mm fired some 1800' away. I’ve enjoyed these recreated scenarios explaining how something could have happened, but in this particular one, a fellow at a distance of roughly six football fields fired a 9mm into the air, which then came down nose first into the victim, with the tip to base perpendicular with the ground.
    Now, I'm well aware these shows don't always adhere to accuracy, but I do want to be certain that the flaw I picked up on was in fact a flaw and not a product of my own misunderstanding.

    Here's a scenario, tell me if I'm mistaken:

    A person fires a handgun round into the sky above, when it eventually lands, it should land nearly base-first with the nose pointed in roughly the same direction as it was when leaving the barrel due to angular momentum imparted by the rifling, correct?

    Following along those same lines, if a rifleman were to engage a target some 2500 meters away (as an extreme example) and were able to adjust his sights appropriately, when the bullet strikes the target, it would strike more so with the side of the nose more so than with the tip of the nose, correct?
    Essentially, if a high-speed photograph were to show the instant this bullet made contact with the target, it would not be protruding at a 90 degree angle from the target, but perhaps closer to a 135 degree angle, again due to the “spin” imparted by the rifling.

    I’ve been under this impression as long as I can remember and it disturbs me that I’ve never bothered to validate that belief.

    Thanks.
     
  2. Father Knows Best

    Father Knows Best Member

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    Nope. That is theoretically possible if you spin the bullet fast enough, but in reality bullets don't spin that fast. A bullet will almost always strike a target nose first. The bullet will have a attitude upon impact that is parallel to the tangent of the trajectory. If the bullet strikes the target at a point beyond its max height, i.e., on the downward slope of its trajectory, then the bullet's nose will be below the horizontal plane.
     
  3. Control Group

    Control Group Member

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    That's an incredibly good question. I feel like I ought to know the answer, too, but I don't.

    My first guess, though, is that it will fall nose down. I only think this because impact-fused artillery shells have the fuse in the nose of the shell, and cannon have rifled barrels. So the shell should have rotational inertia similar to a bullet, but is obviously designed to strike the target nose-first.

    However, even if I'm right, I don't have a good explanation for why rotational inertia doesn't keep the round oriented the way it left the barrel. Here's hoping a better armchair physicist than me (or maybe even a legitimate physicist) weighs in on this.
     
  4. PaladinVC

    PaladinVC Member

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    I'm looking forward to the answer to this question. I saw that episode, too, and wondered why they confused a long lob with a short-range shooting.

    For one thing, the bullet couldn't have been going faster than terminal velocity, and for another I figured the spin of the bullet would impart enough gyroscapic stability that it would go in tail-first.

    Some science person answer this difinitively, please.
     
  5. Father Knows Best

    Father Knows Best Member

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  6. fisherman66

    fisherman66 Member

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    The drag caused by the greater surface area of the rearward section of the bullet would cause it it always be lead by the nose in a low friction environment (or equilly distributed friction environment - not bone or tissue). The spinning force of the bullet is not strong enough to cause a gryroscopic event. Gravity trumps in this case.

    CSI goes to greater lengths than most shows to be accurate, but not always. Ever see the one with the rare GP100? All of a sudden mine is a collector's piece.
     
  7. RavenVT100

    RavenVT100 Member

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    Anything shown on CSI is generally regarded by the real forensics community as being junk science. It's purely fictional and I would not assume anything you see in it is neccessarily accurate.
     
  8. MechAg94

    MechAg94 Member

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    fisherman got it. Air drag will determine the orientation of the bullet.
     
  9. richyoung

    richyoung Member

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    NOT air drag - gyroscopic forces (IF the bullet is not over-stabilized) will cause the long axis of a rotating bullet to stay parallel to it's line of flight as the bullet path arcs to follow a balistic trajectory. Its a phenomenon called "trail", and can be most easily seen in the flight of a football thrown with a spiral, especially in slow motion. You will notice the nose of the football is pointed up as the quarterback thows "the bomb", becomes flat at the top of the arc, and is pointed down when the wide-out catches it, despite the fact that the front and back of the football are essentially aerodynamically identical. Aerodynamic drag IS used to stabilize slugs shot from smoothbore shotguns - but it has to do with the sectional density of the hollow tail vs. the solid head that keeps it pointing the right way - think "sock in a rock"...
     
  10. rhubarb

    rhubarb Member

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    I ain't no engineer nor ballistician, so I don't know if it's possible.

    But, let me get this right: you was watching a teevee show that had something on it about guns and you thought it might be right? Huh. My favorite scene from CSI was when the lady doing an autopsy held up a bullet and said, "It's a 22." The character played by David Caruso replies, "Ah, .22 long rifle for distance." Dum bass. We need to get some folks from THR to get jobs in Hollywood. Even if it's as a janitor. If I was sweeping the floor on the set and I heard that line, I would feel morally obligated to speak up. How is it possible that nobody in the whole studio knew that a .22 LR is not a long distance sniping round?

    1800'? That's what? 3/8 mile? And I have trouble keeping my 9mm in the black at 20 yards. I gotta practice more.
     
  11. Control Group

    Control Group Member

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    Moreover, I sure couldn't tell a .22 LR from a .22 mag just looking at a bullet that's penetrated clothing, skin, and other tissue to lodge inside a corpse.

    On the other hand, to be fair to the show, it wasn't presented as an intentional shooting, it was some jerk firing rounds in his back yard, and sending one off into the sky. I'm pretty sure a 9x19mm round can make it at least that far, if all you're trying to do is get distance.
     
  12. Snowdog

    Snowdog Member

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    Thanks for the explanations, folks. It would appear I was under a false impression for quite some time.
    Thanks for the link, FKB. I plan to print out a hard copy to keep around in case I run into anyone else who believes as I once did.

    The football example was especially helpful, Rich.
     
  13. MachIVshooter

    MachIVshooter Member

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    Sure you can. .22 LR slugs are lead or copper plated lead; .22 mag slugs actually have a jacket. And if the bullet were fairly in-tact, you could differentiate between .22 short/long vs. L.R. as well, based on weight and friction surface.

    That said, any of these television shows that attempt to play out ballistic scenarios usually have more flaws than accurate assessments. I saw an episode of CSI were they stated "handgun rounds penetrate 12 inches of tissue". We all know that's BS. My .25's would be doing well to go 8", while my .50 AE or .454 Casull would likely get 3' +, barring bone impacts. Take it with a grain of salt and enjoy the show for it's drama, not technical accuracy (or lack thereof)
     
  14. twoblink

    twoblink Member

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    From the little aerodynamics I have had; items flying through the sky are "happiest" when they are tear drop shaped.. That means lowest drag possible.

    Why twist rates matter, given a bullet weight, twist rate, (ah triple integral stuff!!) how much mass is from the centerline of the bullet (why a hollow point is suppose to be more stable I believe) a bullet will eventually become unstable. When that's all said and done, a bullet will eventually become unstable, wobble, and then have the pointy end in the rear, because it produces the lowest drag.

    Inaccuracies in CSI? I don't even bother anymore.. I like CSI LV, NCIS, CIS NY, and then CSI Miami if I have to.. in that order.

    There was an episode where a guy got electricuted while in his jeep from a powerline that fell in a storm. Nick Stokes says something to the effect that he should have been protected because of the rubber tires.. Obviously, the writers believe heresay and misnomer vs reality. In that situation, it's like a bird on a high tension wire; electricity travels by the shortest route, and going through you heart ain't it. The rubber at those numbers don't do squat for ya. The electricity gets passed from the car frame, to the closest piece of metal in your car to the ground, the disk brakes, and then into the ground.

    CSI, is like WWF, both are drama first and formost, with reality being an afterthought at best..

    That said, I love Grishem..
     
  15. Red Dragon

    Red Dragon Member

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    Most bullets fired into the air tend not to come down anywhere near as fast as the go going up. I've seen that episode and I honestly don't think the bullet would be traveling fast enough to do as much damage as it did. My father works at the VA hospital in downtown Detroit and during New Year's there tends to be an excessive amount of automatic weapons fire in the downtown area. Several times, my father has gone up to the roof several days later and found a significant quantity of bullets scattered all over the roof. None of them actually penetrate any of the softer waterproofing layers of the roof. I have also never heard any news reports about vehicles or storefronts or any people being significantly damaged or injured by falling bullets.
     
  16. twoblink

    twoblink Member

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    Without a drag co-efficient, if you fired a bullet straight up, and it fell straight down, it would have the same speed as when it left the muzzle. drag is big, but not to the point of serious speed reduction...

    a 9mm is not that powerful, I can't hit much past 25 yards with it. lobbing over 10 houses is difficult as it is...
     
  17. c_yeager

    c_yeager Member

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    The drag is significant, and the "terminal velocity" of the bullet is likely to be a fair amount slower than its velocity when fired.

    According to this balistic calculator http://www.handloads.org/calc/
    a 115grain 9mm RN bullet fired at 1200 fps would be moving at 603 FPS at 600 yards for around 93 ft/lb of energy (the bullet would also be hitting about 800 inches below point of aim).

    This muzzle energy is comparable to a .25acp plinking load under 100 yards and is certainly fatal. According to the CSI episode the recovered bullet had only penetrated about 6 inches, and this minimal penetration is what prompted all the investigation. It actually sounds like the episode was marginally accurate.

    As far as orientation I am inclined to think that a bullet fired at a steep angle would land point first. Remember, this bullet wasnt fired straight up, it was fired at an angle that produced a steep parabolic (ballistic?) arc and the bullet never lost foreward motion, so there is no reason to believe that it would have flipped over.

    Remember that this wasnt an aimed shot, it was an accidental (negligent) shooting, in which a man fired his pistol at a steep angle in the middle of the city.
     
  18. Red Dragon

    Red Dragon Member

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    Forgive me if I am wrong but, isn't the ballistic calculator estimating all information on a bullet fired at a ground target? In the episode, the bullet was basically shot almost straight up. At such an angle as the one fired in the episode, the bullet would have lost just about all of the momentum gained by the actual firing of the bullet and simply fallen back to earth in a fashion similar to simply dropping the bullet from the same altitude. If that was the case, and if I did the calculations right, (which I could have totally screwed up given that its almost 6 am and I made a lot of assumptions) I found that the terminal velocity of a 9mm bullet would be somewhere around 105.4 fps which would give you a bruise and maybe a whelt (sp?). An airsoft springgun fires at about 240 fps. Though, as I said, it's almost 6 am and I've been up since yesterday so I could be way off.
     
  19. Father Knows Best

    Father Knows Best Member

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    When I lived in Phoenix (5-10 years ago), a teenage girl was found dead in her backyard. There was a bullet hole in the top of her head. The police later surmised that some idiot had shot into the air, "what goes up must come down" and she was in the wrong place at the wrong time. The shooter was never found.
     
  20. Red Dragon

    Red Dragon Member

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    here is what I found on a website called "The straight dope"
    ------------------------------------------------------------------------
    Dear Cecil:

    Every so often you see it on the news: streets full of Middle Eastern men indiscriminately firing guns straight up into the air. If I learned anything from physics class, it's that what goes up must come down. I'm certain the returning projectiles don't float harmlessly to earth and wonder how often they plunge into bystanders. --Kathy Johnson, Madison, Wisconsin

    Cecil replies:

    Those Middle Eastern men. You want to shake them and say, guys! Is this the safe and sensible way to celebrate? Can't we just say "hooray!" and "whoa, baby"?

    But you raise a good point. How dangerous is this really? The question is controversial. Let me lay it out point by point.

    Datum 1. At first I thought being struck by a bullet falling straight down would be no worse than getting hit over the head with a two-by-four--not the average guy's idea of fun, but not fatal either. What goes up must come down, but it needn't do so at the same speed. You run up against what's known as "terminal velocity." A bullet fired straight up will slow down, stop, then fall to earth again, accelerating until it reaches a point where its weight equals the resistance of the air. That's its terminal velocity.

    For further insight, we turn to Hatcher's Notebook (1962) by Major General Julian S. Hatcher, a U.S. Army ordnance expert. Hatcher described military tests with, among other things, a .30 caliber bullet weighing .021 pounds. Using a special rig, the testers shot the bullet straight into the air. It came down bottom (not point) first at what was later computed to be about 300 feet per second. "With the [.021 pound] bullet, this corresponds to an energy of 30 foot pounds," Hatcher wrote. "Previously, the army had decided that on the average an energy of 60 foot pounds is required to produce a disabling wound. Thus, service bullets returning from extreme heights cannot be considered lethal by this standard."

    If 30 foot pounds doesn't mean much to you, the bullet made a mark about one-sixteenth of an inch deep in a soft pine board. About what you'd get giving it a good whack with a hammer. Note that we're talking about bullets shot straight up here. If the bullet is fired more or less horizontally, it may not lose much speed before returning to earth and could easily kill someone.

    Still, the question isn't how many people get injured or killed by falling bullets, it's whether such things are possible at all. On further investigation, it appears the 60 foot-pound injury threshold cited by Hatcher may be misleading--a falling bullet's kinetic energy (foot pounds) alone is not a good predictor of the speed it needs to inflict a wound. B. N. Mattoo (Journal of Forensic Sciences, 1984) has proposed an equation relating mass and bullet diameter that seems to do a better job. Experiments on cadavers and such have shown, for example, that a .38 caliber revolver bullet will perforate the skin and lodge in the underlying tissue at 191 feet per second and that triple-ought buckshot will do so at 213 feet per second.

    Mattoo's equation predicts that Hatcher's .30 caliber bullet, which has a small diameter in relation to its weight, will perforate the skin at only 124 feet per second. It's easy to believe that such a bullet falling at 300 feet per second could kill you, especially if it struck you in the head.
    --CECIL ADAMS
     
  21. c_yeager

    c_yeager Member

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    Now that i actually look at the number i posted i think you may be right. If you take into account the drop (about 800inches (22 yards)) and the distance (600 yards) it would show that the weapon was fired at only 2.1 degrees above level. (or 120 MOA or 480 'clicks' on your 1/4MOA adjustable target scope) (the bullet drop figure *should* indicate where the POA must be in order to hit the target, this point is thus directly above the target and allows one to draw a right triangle to figure this out).

    Since we know that the weapon was fired at an angle much steeper than this, i think you are corect that the projectile would be moving at it's terminal velocity, rather than the figure that i posted. This means that it probably wouldnt have killed the victim, and probably wouldnt have left much more than a bruise (if your velocity is correct i think it comes out to about 12ft/lbs of energy)

    The numbers i posted do give us an interesting perspective on how far away a missed shot can end up though. Shooting over your targets head with a 9mm could potentially kill someone 600 yards away, interesting to know, but completely irrelevant to our CSI discussion.
     
  22. Red Dragon

    Red Dragon Member

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    perhaps when they were writing the episode they were thinking more towards a rifle bullet. Given the very different shapes and weights of rifle bullets, their terminal velocity can be quite different from a 9mm bullet and could come down with a relatively more significant amount of force. There have been reports of soldiers in Iraq getting injuries ranging from bruises to fatalities from celebratory fire of weapons like AK-47s of course there are a lot of factors that we don't know of. (i.e. because temperature effects the viscosity and density of air, as well as altitudes having different levels, the terminal velocity could be drastically changed)
     
  23. pete f

    pete f Member

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    It is TV, it is fiction. nuf said
     
  24. GaryM

    GaryM Member

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    Bullets will stay at the same attitude at the end of their trajectory as they were at the beginning. I.E. fired straight up they will come back down base first.
    Bullets will reach a certain velocity in free fall and not exceed it, this is called terminal velocity and is a function of gravity and aerodynamic drag. Of course in a vacuum the speed will be far greater since there will be no forces acting to slow or stop the acceleration.
    The attitude in which and object will fly in free flight is determined by its center of pressure and center of mass. Center of mass will always be directly forward of the center of pressure in free fall if the object has enough velocity for it to reach a speed where it can stabilize.
    As for pistol bullets being nose heavy, maybe round nose are but hollow points will always be heavier to the rear and as such will not be aerodynamically stable without others forces involved such as rotational velocity giving them gyroscopic stability.

    Thank you, please drive through....

    Oh yeah, CSI is full of ????. I saw them once shoot a pistol into a bullet box so they could exam a fired bullet.
    The bullet capture box was just sitting on a table in the middle of the lab. No safety walls or anything else around, just a table in a lab in an office building. Can anyone ever possibly see that happening in reality with out every damn safety agency ever created going completely bonkers?
     
  25. Joejojoba111

    Joejojoba111 Member

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    "Anything shown on CSI is generally regarded by the real forensics community as being junk science. It's purely fictional and I would not assume anything you see in it is neccessarily accurate."

    And any story they have is either butchered from real life, or butchered from other shows, or butchered from other shows that accurately represented real life stories.

    The real story was on 'The New Detectives'. It's a show that was around before CSI, it doesn't show hot chicks wearing skin-tight pants solving crimes, though, so it can't compete to the masses.

    The real story was that a felon and his buddy were shooting at his buddy's large back yard with a magnum handgun at bottles and such for targets. A mile away or something a man sitting in his lawn chair waiting for the July 4th fireworks slups over and is shot dead, bullet penetratign down and across his torso from (right?) shoulder to opposite ribcage.

    Police go around and ask questions, but no-one in neighborhodo knows anything. Finally the police figure out that it was a pistol and the bullet was arcing downwards, and when the felon reads this in the paper he comes forward and says he and his buddy convinced his girlfriend to fire the handgun, and she only fired once, but they thought it might have recoiled funny or been pointed up or somethign. They thought she just missed the target, no-one would have thought otherwise. When police reconstructed bullet path it passed within inches of over a dozen obstacles, chimneys trees lampposts, the odds of this shot ever reaching the park were incredible, the odds of hitting the man were incredible, and the odds they would kill him in such a perfect manner, incredible.

    IMO it's one of those natural disasters where they have to blame god, because it really looks like that was who's at fault!
     
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