Harnser Posted March 31, 2009 Author Report Share Posted March 31, 2009 A human falling from 10K feet will travel at a terminal velocity IRo 127MPH a bullet is IRo 10x more dense than the human body and is much more stream lined (less drag) therefore its terminal velocity will be significantly more than that of a human. I would not expect the terminal velocity to be 10 times that of a human but at least two to three times more. Of interest at 100000 feet (thinner Air) a human will free fall at up to 600mph and it has been done!! Isnt it true that nothing can free fall faster than terminal velocity .But an object can fall slower than terminal velocity depending on shape wind resistance ect . Harnser , Quote Link to comment Share on other sites More sharing options...
al4x Posted March 31, 2009 Report Share Posted March 31, 2009 (edited) Isnt it true that nothing can free fall faster than terminal velocity .But an object can fall slower than terminal velocity depending on shape wind resistance ect . Harnser , I believe thats what that clever fellow Isaac Newton prooved with his apples If you're bored have a look at this http://www.youtube.com/watch?v=KUzQQKhXJzY Edited March 31, 2009 by al4x Quote Link to comment Share on other sites More sharing options...
fullbore Posted March 31, 2009 Report Share Posted March 31, 2009 Again not vertically/straight up.If they are fired at a high angle they will come down at a similar steep angle. Allowing of course for wind drift, the turning of the planet Gravity, etc all of which have a bearing on even long range shots Quote Link to comment Share on other sites More sharing options...
fullbore Posted March 31, 2009 Report Share Posted March 31, 2009 He was under the impression that a bullet (say .308 150 grn ) fired vertically into the air would come back down to earth with enough velocity to kill any body that it struck . I don't understand what you are trying to say here, while the squaddy wouldn't have had a spirit level to prove perfect perpendicularity, the gun finished up shooting into the air at what could have been vertical on the fatal shot. There is another instance in the book of a trainee forensic scientist who didn't follow procedure and fire a single round first, instead he filled the magazine and cocked the gun, which due to a faulty sear, went off, walked up while emptying the mag and shot himself dead through the chin, so guns do walk vertical while being fired if not kept under control Quote Link to comment Share on other sites More sharing options...
mr smith Posted March 31, 2009 Report Share Posted March 31, 2009 So the squaddie was seven miles away from where the fatal bullet landed,now while i agree that there would be several rounds fired as the muzzle climbed under full auto, the angle of these rounds may well have allowed a bullet to cover such a distance(and there have been many documented cases of this) i doubt and i ain't no expert but i cannot see how a bullet fired perfectly straight up and thats what i thought was the question could have travelled seven miles. Quote Link to comment Share on other sites More sharing options...
glogin Posted March 31, 2009 Report Share Posted March 31, 2009 I think the best way to find out who is right is to arrange an experiment It would make a great youtube movie too ;-) Quote Link to comment Share on other sites More sharing options...
al4x Posted March 31, 2009 Report Share Posted March 31, 2009 (edited) sounds like Dads Army with the boys in their tin helmets thats assuming fullbore doesn't think he'll get penetration through his helmet Edited March 31, 2009 by al4x Quote Link to comment Share on other sites More sharing options...
casts_by_fly Posted March 31, 2009 Report Share Posted March 31, 2009 Isnt it true that nothing can free fall faster than terminal velocity .But an object can fall slower than terminal velocity depending on shape wind resistance ect . Harnser , harnser, Yes, the terminal velocity of an object is the fastest that it can fall through a medium. Terminal velocity will depend on the medium (air, water, oil, etc, specifically the density of the fluid), the mass of the object, the frontal area, and the drag coefficient. Basically, the force pulling the object down (the force of gravity for an object in freefall) will be equal to the force of air resistance. In the absense of air resistance, an object would continue to accelerate under the force of gravity and there would be no terminal velocity. Air resistance (more accurately fluid resistance) is proportional to velocity squared- the faster you go, the more resistance there is. Each object in freefall will have a different terminal velocity. A feather has a very low terminal velocity because it has a very high drag function and high frontal area for the amount of mass. Another way to think about it is the ballistic coefficient. In bullets, the BC takes into account the mass, frontal area (both combine to form the sectional density) and the drag function (shape coefficient). The higher the BC, the faster the terminal velocity would be of a bullet in freefall. The 1920 US army study used 150 gr, 30 cal spitzer bullets and calculated an impact velocity of 300 fps on the way back down. That is about 30 ft-lb energy. The army conclusion was that it would hurt, but not kill. An unfortunate soldier that was looking at the bullet when it struck (i.e. in the head) might think differently, but a body should wouldn't have necessarily killed you. Now if you were to use a different bullet with a higher BC you'd get more speed and more energy. Also, when you start using heavier bullets there will be more penetration at the same energy level. So the likelihood of death increases. Long story short, it is possible, but only under the right conditions. Thanks, Rick Quote Link to comment Share on other sites More sharing options...
Harnser Posted March 31, 2009 Author Report Share Posted March 31, 2009 Thank you Rick , Very informative . Harnser . Quote Link to comment Share on other sites More sharing options...
fullbore Posted March 31, 2009 Report Share Posted March 31, 2009 sounds like Dads Army with the boys in their tin helmets thats assuming fullbore doesn't think he'll get penetration through his helmet There's nothing penetrating my tinfoil helmet I'll have you know, I 'm safe from everything, even the thought rays Quote Link to comment Share on other sites More sharing options...
Vince Green Posted April 1, 2009 Report Share Posted April 1, 2009 Some of the earliest ballistic tests on old cannons were carried out by firing them vertically in the air and counting how long it took before the cannonball landed back on earth. The question is where would you stand while you were waiting? A cannon was fairly low in terms of muzzle velocity, a 7.62 bullet would be a different thing altogether. Lead shot just falls out of the sky like hailstones when it fired upward. A spent rifle bullet would not come back down at 2800fps but it could cartainly injure you. Quote Link to comment Share on other sites More sharing options...
Rem223 Posted April 2, 2009 Report Share Posted April 2, 2009 As it happens this very subject was covered by Robert Rinker in the last issue of the Varmint Hunter. His calculations and the US army research Rick mentions above showed the impact velocity of a 150gr bullet fired vertically would be around 300fps. I wouldn't want to be hit by that, but as to whether it could kill someone I have my doubts it certainly could inflict a nasty injury. BTW he states that the maximum range of a 7.62mm round is 4,400yds or 2 1/2 miles when fired at 30 degrees so the story of someone being killed at seven miles sounds dubious to me. Quote Link to comment Share on other sites More sharing options...
The Burpster Posted April 2, 2009 Report Share Posted April 2, 2009 I think the best way to find out who is right is to arrange an experiment It would make a great youtube movie too ;-) who's getting the job of running around with the vertically pointing chrono trying to get said round to fall though it? I for one am not volunteeriong for that job...... Quote Link to comment Share on other sites More sharing options...
fullbore Posted April 2, 2009 Report Share Posted April 2, 2009 BTW he states that the maximum range of a 7.62mm round is 4,400yds or 2 1/2 miles when fired at 30 degrees so the story of someone being killed at seven miles sounds dubious to me. Isn't TV wonderful, as I mentioned earlier, Brian J Heard was Britains top forensic scientist, he documentd the case and yet you find his conclusions dubious? Prefering instead the opinion of some TV presenter, the mind boggles Quote Link to comment Share on other sites More sharing options...
mr smith Posted April 2, 2009 Report Share Posted April 2, 2009 Isn't TV wonderful, as I mentioned earlier, Brian J Heard was Britains top forensic scientist, he documentd the case and yet you find his conclusions dubious? He wasn't involved in the birmingham six case was he. Quote Link to comment Share on other sites More sharing options...
casts_by_fly Posted April 2, 2009 Report Share Posted April 2, 2009 fullbore, Physics does not permit a bullet to travel 7 miles unaided (at least not one we're going to fire from a gun any of us have). From the BC of the bullet and the muzzle velocity you can calculate the maximum range. It is pretty standard stuff and most all ballistics programs have the ability. Seven miles is a really long way in bullet terms. As rem said, 2-3 miles is about the normal for a normal bullet. As an example, try running a .308" Berger VLD 210 grain at 4000 fps. That is a super heavy for caliber round of about the most optimal shape you'll get for retaining energy and minimizing drag. And, that is driving it faster than any cartridge I know of is capable of doing. You get a maximum range of 3.99 miles. A Lapua .338 250 gr silver scenar at 4k would do an extra 325 yards. In fact a 500 gr bullet designed with a BC of 1 moving at 4K will still only do 5.5 miles. So from a sheer physics perspective, the 7 mile claim is highly suspect. To put it another way, a 150 gr FMJ BT would require a muzzle velocity higher than solid propellants can thermodynamically achieve (6500 fps I believe is the gas expansion limit) to go 7 miles, if it can even be propelled fast enough. At generous 308 velocities (3000 fps) that bullet can go 2.5 miles or so. Again, 7 miles is highly suspect. I don't doubt that the 'expert' claimed those things. I'm saying that he was either wrong on his distances or there was some interveneing factor that caused the bullet to bounce a couple times (without tumbling) and continue on its path. It didn't get there on the fly though, that is for certain. Thanks, Rick Quote Link to comment Share on other sites More sharing options...
cubix Posted April 2, 2009 Report Share Posted April 2, 2009 Fired straight up, eventually it will stop with no momentum and start to fall back of its own accord. Same as you standing on top of a tower block and dropping it by hand. It would have no momentum left from the power of the shot, only what gravity would give it. It's aerodynamics will limit the speed so it would not accelerate indefinitely and probably reach terminal velocity within a few hundred feet. I reckon it would hurt and sting but not kill. It would lose it's spin and start to tumble, slowing it further. All things want to fall at the same speed - remember the hammer and feather demo by the astronought on the moon? In the mythbusters episode the round barely broke the surface of the dried mud where they were, that was 45 cal hand gun round. Heavier than a 308 round ?? and it had plenty of time to get up to max falling speed. MYTH BUSTED. Quote Link to comment Share on other sites More sharing options...
fullbore Posted April 2, 2009 Report Share Posted April 2, 2009 In the mythbusters episode the round barely broke the surface of the dried mud where they were, that was 45 cal hand gun round. Heavier than a 308 round ?? and it had plenty of time to get up to max falling speed. MYTH BUSTED. Then it's high time the ginger and stupid big tached Yank were called to court as "expert" witnesses instead of the people with the training and expertise, I despair, I really do Quote Link to comment Share on other sites More sharing options...
al4x Posted April 2, 2009 Report Share Posted April 2, 2009 Then it's high time the ginger and stupid big tached Yank were called to court as "expert" witnesses instead of the people with the training and expertise, I despair, I really do you despair or you've got the facts wrong, if the bullet won't physically travel 7 miles either you or the expert has one or more facts wrong. One things for sure if you fire it vertically I have a little trouble seeing how it travels 7 miles, unless there was a hurricane or it deflected off a 747 on the way up sat on the wing for a bit and then fell off Quote Link to comment Share on other sites More sharing options...
wymberley Posted April 2, 2009 Report Share Posted April 2, 2009 HI, all, Think I'm right in saying that a bullet/shrapnel strike of 60ft lbs is deemed sufficient to incapacitate a soldier. Quote Link to comment Share on other sites More sharing options...
casts_by_fly Posted April 2, 2009 Report Share Posted April 2, 2009 wymberley, that was the standard the the Army ordinance survey used as the amount of energy to kill a soldier with a bullet. When the energy from the falling bullet was calculated to be 30 ft-lb, they concluded that it wouldn't kill, just wound. thanks rick Quote Link to comment Share on other sites More sharing options...
Rem223 Posted April 3, 2009 Report Share Posted April 3, 2009 Isn't TV wonderful, as I mentioned earlier, Brian J Heard was Britains top forensic scientist, he documentd the case and yet you find his conclusions dubious? Prefering instead the opinion of some TV presenter, the mind boggles hmm1.gif hmm1.gif Actually I did not quote "some tv presenter" the article was written by Robert A Rinker. He has written several books on ballistics for what it's worth. http://catalog.ebay.com/Understanding-Fire...Z496166QQ_tabZ2 Quote Link to comment Share on other sites More sharing options...
fullbore Posted April 3, 2009 Report Share Posted April 3, 2009 you despair or you've got the facts wrong, if the bullet won't physically travel 7 miles either you or the expert has one or more facts wrong. One things for sure if you fire it vertically I have a little trouble seeing how it travels 7 miles, unless there was a hurricane or it deflected off a 747 on the way up sat on the wing for a bit and then fell off :unsure: I have given you the book, the authors name and the ISBN number , Now I know that you don't like UFO tales and the like but, this is documented evidence from a leading forensic scientist, if he has got it wrong then thats another matter. What I despair about is people accepting as gospel the word of mythbusters above an accredited expert Quote Link to comment Share on other sites More sharing options...
Doggone Posted April 3, 2009 Report Share Posted April 3, 2009 was talking to a friend today about rifle ballistics . He was under the impression that a bullet (say .308 150 grn ) fired vertically into the air would come back down to earth with enough velocity to kill any body that it struck . I was and am of the opinion that any said bullet dropping from say 5,000 feet could only fall at a maxim speed of terminal velocity ( approx 125 miles per hour ) and would not neccesarily be fatal even if you were struck on the head . Who is right . Harnser . Could be wrong, but 125mph is 183 fps, which, with a 150 gn. bullet would give 11.16 ft.lbs. of energy. A bit like being shot at point blank with a 12 ft.lb. air rifle. Not pleasant !! Andy Quote Link to comment Share on other sites More sharing options...
Peter De La Mare Posted April 3, 2009 Report Share Posted April 3, 2009 (edited) Mythbusters did this experiment a while ago. Busted if fired straight up. Plausible if fired at an angle. http://mythbustersresults.com/episode50 Edited April 3, 2009 by Peter De La Mare Quote Link to comment Share on other sites More sharing options...
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