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Thread: Falling bullets

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    State Researcher .40 Cal's Avatar
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    I know that one of the stupidest things one can do is to shoot up into the air, and I condemn it in every way. This said, does anyone have any facts on the lethality of this?At what rate does the bullet come down? Physically it would be impossible for it to come down at the same speed it left the firearm.

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    Well, barring air resistance it will come down at the exact same speed it left the gun. If you shoot it straight up it stops spinning and starts tumbling end over end, drastically reducing it's terminal velocity. If you put a little angle on it, it follows an arc and keeps spinning. It will only move as fast as it's terminal velocity, but for a bullet traveling straight through the air that's pretty damn fast (yes, PDF is a standard unit of measure).

    Edit:
    A quick googling isn't bringing up anything conclusive. There was an episode of Mythbusters where they tested this, and their conclusion was that a bullet fired straight up is unlikely to do anything but leave a welt, but one with an arc to it can possibly be lethal.

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    A bullet will start to lose it's muzzle velocity after it leaves the barrel, due to atmosheric resistance and gravity.

    A bullet with a muzzle velocity of 1000 Ft per second equals 681.8 MPH. My guess is that a bullet will not fall back to earth at the speed it left the barrel of the gun, but more like around 150 to 200 MPH. I don't want to be standing under one when it comes back down.

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    Yeap, if fired straigth up overhead the worst that could probably happen is a cracked car windshield, small dent in a car roof or a nasty lump on the top of the head possibly breaking the skin, but nothing fatal. Fired in an arc and depending on the caliber can be fatal over3 miles. I believesometime in the last year or 2someone on a crab boat on the James River about 1-1/2 miles off shore from the Ft Eustis firing range was wounded by a small caliber round believed to have come from the range.
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    FogRider wrote:
    Well, barring air resistance it will come down at the exact same speed it left the gun. If you shoot it straight up it stops spinning and starts tumbling end over end, drastically reducing it's terminal velocity.

    Actually, I think the upward motion would cease long before it would stop spinning. Bullets can spin upwards of 300,000 RPM + for rifle bullets, not sure about pistol bullets. Since that spin has almost no resistance, it's going to spin quite a while...

    From what I've read, a bullet fired straight up would come back down, still spinning, backwards, at whatever the terminal velocity of the bullet is.

    ...Orygunner...

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    .40 Cal wrote:
    I know that one of the stupidest things one can do is to shoot up into the air, and I condemn it in every way. This said, does anyone have any facts on the lethality of this?At what rate does the bullet come down? Physically it would be impossible for it to come down at the same speed it left the firearm.
    Everything that falls speeds up until it hits itsterminal velocity (air resistance overpowering gravity acceleration). Bullets are veryaerodynamic, so you'd think they would drop pretty fast.



    3 1/2 seconds searching google yielded this:

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



    Based on the results of these tests it was concluded that the bullet return velocity was about 300 f.p.s. For the 150 gr. bullet this corresponds to an energy of 30 foot pounds. Earlier the Army had determined that, on the average, it required 60 foot pounds of energy to produce a disabling wound. Based on this information, a falling 150 gr. service bullet would not be lethal, although it could produce a serious wound.


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    Regular Member IanB's Avatar
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    Orygunner wrote:
    From what I've read, a bullet fired straight up would come back down, still spinning, backwards, at whatever the terminal velocity of the bullet is.

    ...Orygunner...
    Also, bullet weight must be taken into consideration.

    Would you rather be hit by a .22 at terminal velocy or a 10 pound cannon ball dropped from 50 feet? The .22 will likely bounce off your head and the cannon ball...well...

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    Thanks for the info guys.

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    .40 Cal wrote:
    I know that one of the stupidest things one can do is to shoot up into the air, and I condemn it in every way. This said, does anyone have any facts on the lethality of this?At what rate does the bullet come down? Physically it would be impossible for it to come down at the same speed it left the firearm.
    The show mythbusters did an episode on this. The terminal velocity they found was not enough to kill, but as some have said produce a nice lump on the noggin.

    They did show that a bullet fired at some angle less than vertical could produce a more devastating injury. I can't remember what the angle was for a fatal injury.
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    There have been a few reports over the years of people being injured and even killed by bullets supposed to have been carelessly fired into the air. My belief as to why there are not more reports of this is that most of these bullets simply don't hit anybody. I have had one of these bullets leave a nice dent in the bed of my old pickup before, so I have no doubt that they could be fatal. On a somewhat related note, I have been hit many times by 'shot' from shotguns while bird hunting with no injuries whatsoever... (no, I haven't been hunting with Dick Chaney)

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    Be careful about making "scientific" assumptions! Very few rounds shot in the air go straight up and straight down.

    I have a very good friend in Croatia that was hit in the head by a celebratory bullet while standing in the middle of the main square in Zagreb on New Years Eve. The bullet entered his head and caused massive damage, resulting in partial paralysis to the left side of his body.

    Another friend of mine was hit by a 5.56 round fired from the KD range at Ft. Devens. he was over 1 mile away and on the opposite side of a large hill. The bullet hit a plastic target, was deflected upwards on a trajectory that sent it over the hill and into my buddie's ankle, resulting in permanent damage. He wasn't able to walk for 2 years and went through numerous reconstructive surgeries.

    Granted, the second case was a freak event, but the in the first, my friend is lucky to be alive. Bullets do things that cannot be explained once they leave the barrel. NEVER SHOOT INTO THE AIR!

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    .40 Cal wrote:
    I know that one of the stupidest things one can do is to shoot up into the air, and I condemn it in every way. This said, does anyone have any facts on the lethality of this?At what rate does the bullet come down? Physically it would be impossible for it to come down at the same speed it left the firearm.
    The lethality depends entirely on the angle and that is the crux of the matter. Without some type of jig set to ensure a vertical trajectory plus or minus a few degrees, it is almost impossible to determine vertical without a point of reference to aim against. Anything much off of absolute vertical has a high risk of causing severe to lethal damage if it hits someone. There are few places that are remote enough anymore to allow safe shooting into the air even with a method to ensure a vertical trajectory.
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    Gator5713 wrote:
    There have been a few reports over the years of people being injured and even killed by bullets supposed to have been carelessly fired into the air. My belief as to why there are not more reports of this is that most of these bullets simply don't hit anybody. I have had one of these bullets leave a nice dent in the bed of my old pickup before, so I have no doubt that they could be fatal. On a somewhat related note, I have been hit many times by 'shot' from shotguns while bird hunting with no injuries whatsoever... (no, I haven't been hunting with Dick Chaney)
    I think it is probably pretty rare for someone to be able toshoot a perfect 90 degrees from the groundvertical shot. It would probably be safe to assume that the further away from true vertical you get, the more of the initial energy from the powder remains with the bullet. There would be some angle where neary every shot fired would be potentially lethal if it hit someones head, maybe 45 degrees (absolute wild a$s guess).

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    Decoligny wrote:
    Gator5713 wrote:
    There have been a few reports over the years of people being injured and even killed by bullets supposed to have been carelessly fired into the air. My belief as to why there are not more reports of this is that most of these bullets simply don't hit anybody. I have had one of these bullets leave a nice dent in the bed of my old pickup before, so I have no doubt that they could be fatal. On a somewhat related note, I have been hit many times by 'shot' from shotguns while bird hunting with no injuries whatsoever... (no, I haven't been hunting with Dick Chaney)
    I think it is probably pretty rare for someone to be able toshoot a perfect 90 degrees from the groundvertical shot. It would probably be safe to assume that the further away from true vertical you get, the more of the initial energy from the powder remains with the bullet. There would be some angle where neary every shot fired would be potentially lethal if it hit someones head, maybe 45 degrees (absolute wild a$s guess).
    I believe that the issue is the horizontal and verticalvelocity.

    Let's assume there is no wind. and you're firing a bullet at 1000 fps. The only forces that can work on the bullet are gravity and air resistance.

    If you fire the bullet straight up (vertically),Gravity and air resistance will overcome the velocity, and it will fall back towards the ground, eventually obtaining terminal velocity (I think someone said 300fps?) on the way back down.

    Take the other extreme, and fire it perfectly horizontally. Although gravity will be pulling the bullet down towards the ground, the only factor actually slowing the bullet will be air resistance.

    So I would think, if you fire a bullet at say, a 80 degree angle (10 degrees from straight up), you're going to have the bullet moving at say, 800 FPS vertically, and 150 FPS horizontally (I'm not doing any math, I'm just guesstimating). Gravity is pulling the bullet down, but the only thing slowing the horizontal movement is wind resistance. When the bullet strikes the ground, it will be travelling at terminal velocity (300fps down) but probably still close to the original horizontal velocity (maybe 70-80 fps?)

    Take a 70 degree angle, the bullet is travelling up at maybe 600 fps, but horizontally at 300fps. when it comes down, it will be coming down at 300fps, but still horizontally at over 200fps, so somewhere around 400-500 fps total velocity.

    I'm just guesstimating all this stuff, but it makes sense to me. I wouldn't expect a bullet to lose much horizontal velocity when fired upwards at an angle, because the only thing slowing it down horizontally is air resistance, while gravity has a greater affect on the vertical velocity.

    ...Orygunner...

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    nakedshoplifter wrote:
    SNIP Would you rather be hit by a .22 at terminal velocy or a 10 pound cannon ball dropped from 50 feet? The .22 will likely bounce off your head and the cannon ball...

    Would bounce off Tomahawk's hard-core mohawk!

    (Sorry, Tommy. Couldn't resist. )



    Edited to Add: I seem to recall hearing that a certain celebration in the Middle East resulted in a number of injuries. Celebratory gun fire into the air, lots of it. Maybe something over kicking somebody out of Beirut or something. Its been a while.

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    Orygunner wrote:
    FogRider wrote:
    Well, barring air resistance it will come down at the exact same speed it left the gun. If you shoot it straight up it stops spinning and starts tumbling end over end, drastically reducing it's terminal velocity.

    Actually, I think the upward motion would cease long before it would stop spinning. Bullets can spin upwards of 300,000 RPM + for rifle bullets, not sure about pistol bullets. Since that spin has almost no resistance, it's going to spin quite a while...

    From what I've read, a bullet fired straight up would come back down, still spinning, backwards, at whatever the terminal velocity of the bullet is.

    ...Orygunner...
    IIRC the mythbusters episode demonstrated impact holes in the desert with similar dimensions to a bullet on it's side, as would be expected if the bullet were tumbling.

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    Bullets fired into the air during celebrations return at a speed fast enough to penetrate the skin and cause internal damage to other organs in the path of the migrating bullet. The bullet’s velocity required for skin penetration is between 148 and 197 feet per second. A velocity of less than 200 feet per second, which is easily obtained by a celebratory gunfire, is capable of fracturing bone and even causing intracranial penetration [4]. Spent bullets have the capability of reaching up to 600 feet per second during their downfall, and thus they have the ability to inflict damage to multiple body cavities [4]. The larger caliber bullets (ie, .45-caliber) reach a higher terminal velocity compared with the smaller caliber bullets (ie, .30-caliber), because of the proportion of their weight to their diameter [4]. Terminal velocity is difficult to calculate with falling bullets because wind resistance and updrafts can cause a spent bullet to land miles away from the initially fired site [2].
    http://ats.ctsnetjournals.org/cgi/content/full/83/1/283



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    "Data show the 77% of reported celebratoryfiring results in injury to the head, 12% to the shoulder, 5%to the upper back, 2% to the posterior chest and neck, respectively,and 1% to the upper arm, leg, and foot each"

    :what:

    Makes perfect sense that a large number of all celebratory firing resulting in an injury are going to impact the head, but 77%? Wow. Nice article.

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    Orygunner wrote:
    I believe that the issue is the horizontal and verticalvelocity.


    Correct. I'm too lazy, but if the OP wants a scientific answer it's as simple as drawing a free-body diagram to understand what forces are acting in what directions. Then you can look up the equations and solve for exactly how fast it'll be going when it finally hits the ground. It's not as complicated as it sounds, it's highschool level physics. It just takes someone that's non-lazy and has some free time, so.... not me. :P



    http://physics.wku.edu/phys201/Infor...eDiagrams.html


    This is a good and easy to understand explanation.

    http://www.fortunecity.com/greenfiel...le_motion.html

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    AWDstylez wrote:
    It just takes someone that's non-lazy and has some free time, so.... not me. :P
    Wow. You just described exactly why I haven't done it.

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    Someone wrote:
    Bullets can spin upwards of 300,000 RPM + for rifle bullets, not sure about pistol bullets.
    Sorry, that just doesn't sound right.

    Twist is expressed as 'one in ten inches' for instance. Just doing an order of magnitude estimate gives 10, 000 rpm. One twist in a ten inch barrel. The bullet takes a millisecond at a thousand feet per second to travel the ten inch barrel and acquire its angular momentum.

    Further, and for this I have no 'formula' in my head, I doubt lead and likely steel would withstand the centripetal forces of 300,000 rpm and would disintegrate.

    Lead yield strength is 12 MPa Alloy 514 yield strength is 760 MPa. '10^4 sec^-1' and '3 x 10^5 sec^-1'. R = 0.5 cm.


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    To much trouble finding the bullet that way. I have enough trouble finding those small
    estes rockets, and they are huge next to the bullet.
    Guess if you used a tracer round you would have at least proof it went straight up.
    I found the best way to get a feel for the reality of them is skip a bullet off of water.
    The timing is just like a stone, but the skips are massive distances. Never got more
    than 4 before running out of water.

    Besides with the fantastic homeland security we have, they would probably charge
    you with praticing for an airline terror attack.

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    Doug Huffman wrote:
    Someone wrote:
    Bullets can spin upwards of 300,000 RPM + for rifle bullets, not sure about pistol bullets.
    Sorry, that just doesn't sound right.

    Twist is expressed as 'one in ten inches' for instance. Just doing an order of magnitude estimate gives 10, 000 rpm. One twist in a ten inch barrel. The bullet takes a millisecond at a thousand feet per second to travel the ten inch barrel and acquire its angular momentum.

    Further, and for this I have no 'formula' in my head, I doubt lead and likely steel would withstand the centripetal forces of 300,000 rpm and would disintegrate.

    Lead yield strength is 12 MPa Alloy 514 yield strength is 760 MPa. '10^4 sec^-1' and '3 x 10^5 sec^-1'. R = 0.5 cm.

    OK. Let's take a common rifle bullet:

    223 Remington (5.56x45mm) -- 62 gr FMJ (steel core), 3020 fps, 1255 ftlbs

    We'll figure it fora barrel with a 1 in 12" Twist first to make the math easier.

    1 twist per foot, x 3020 Feet per Second = 3020 Revolutions Per Second.

    3020 x 60 (seconds per minute) = 181,200 RPM.

    A 1 in 7" Twist (not uncommon for a .223 barrel) would push that same bullet to over 310,000 RPM.

    I had no idea bullets spun at such a high RPM either, until I read John Ross's Unintended Consequences (I can't recommend that book enough). Fictional novel, but a lot of factual informationthrown in. One character has a custom varmint rifle that does have such a high twist and high velocity that about 1 in 10 bullets DOES just desintegrate mid-air.

    ...Orygunner...


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    Orygunner wrote:
    Doug Huffman wrote:
    Someone wrote:
    Bullets can spin upwards of 300,000 RPM + for rifle bullets, not sure about pistol bullets.
    Sorry, that just doesn't sound right.

    Twist is expressed as 'one in ten inches' for instance. Just doing an order of magnitude estimate gives 10, 000 rpm. One twist in a ten inch barrel. The bullet takes a millisecond at a thousand feet per second to travel the ten inch barrel and acquire its angular momentum.

    Further, and for this I have no 'formula' in my head, I doubt lead and likely steel would withstand the centripetal forces of 300,000 rpm and would disintegrate.

    Lead yield strength is 12 MPa Alloy 514 yield strength is 760 MPa. '10^4 sec^-1' and '3 x 10^5 sec^-1'. R = 0.5 cm.

    OK. Let's take a common rifle bullet:

    223 Remington (5.56x45mm) -- 62 gr FMJ (steel core), 3020 fps, 1255 ftlbs

    We'll figure it fora barrel with a 1 in 12" Twist first to make the math easier.

    1 twist per foot, x 3020 Feet per Second = 3020 Revolutions Per Second.

    3020 x 60 (seconds per minute) = 181,200 RPM.

    A 1 in 7" Twist (not uncommon for a .223 barrel) would push that same bullet to over 310,000 RPM.

    I had no idea bullets spun at such a high RPM either, until I read John Ross's Unintended Consequences (I can't recommend that book enough). Fictional novel, but a lot of factual informationthrown in. One character has a custom varmint rifle that does have such a high twist and high velocity that about 1 in 10 bullets DOES just desintegrate mid-air.

    ...Orygunner...
    RPM =/= RPS My apologies.

    I wonder what twist my .17 Remington had that shot at 5050 fps. The centripetal force goes down with radius of gyration.

    I just looked through my Handbook of Physical Calculations and probably saw the solution but in too terse terms to recognize. Maybe I'll rummage though my Halliday, Resnick and Walker.

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    The following is from Mythbusters;
    [edit] Episode 50 – "Bullets Fired Up"
    • Original airdate: April 19, 2006

    edit] Bullets Fired Up



    Myth statement
    Status
    Notes

    Bullets fired into the air maintain their lethal capability when they eventually fall back down.
    Busted , Plausible, and Confirmed
    In the case of a bullet fired at a precisely vertical angle (something extremely difficult for a human being to duplicate), the bullet would tumble, lose its spin, and fall at a much slower speed due to terminal velocity and is therefore rendered less than lethal on impact (the Busted rating). However, if a bullet is fired upward at a non-vertical angle (a far more probable possibility), it will maintain its spin and will retain enough energy to be lethal on impact (the Plausible rating). Because of this potentiality, firing a gun into the air is illegal in most U.S. states, and even in the states where it is legal, it is not recommended by the police. Also the MythBusters were able to identify two people who had been injured by falling bullets, one of them fatally (the Confirmed rating). To date, this is the only myth to receive all three ratings at the same time.




    http://en.wikipedia.org/wiki/MythBusters_%28season_4%29

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