adamT 0 #26 October 10, 2003 Quote In thinking about this I think a good study to look at would be those done by NASA on the debris in space and how things as minute as a grain of sand can have on inanimate materials. That is in a vacume where there is no terminal velocity. Doesn't apply to this discussion. Quote Share this post Link to post Share on other sites
bmcd308 0 #27 October 10, 2003 The tumbling at 200m plus is caused by turbulence as the bullet goes subsonic. The oft-discussed tendency of 223 rounds to tumble in tissue is the result of the fact that they are so long and skinny that their center of gravity is almost never exactly on the axis of the bullet, which makes them "wobble" in the air as they spin around their cg rather than their long axis. If they hit soft tissue while wobbling, the off-axis force on the bullet causes it to start tumbling. 5.56 NATO 62gr bullets destabilize quickly out of older M-16s with 1 in 12 twist barrels, because the barrels were designed for 55 gr ammo. That is why newer 5.56 uppers typically have tighter barrels (1 in 9) to stabilize heavier bullets. Agreed that crappy guns (particularly crappy guns with rifle twists unsuitable for the ammunition fired) result in all kinds of bizarre downrange bullet behavior. In theory, a perfect bullet fired straight up with no wind should fall back down the barrel base first, still spinning at almost the same rate as when it was fired, because there is very little laminar friction to slow its spin once fired. In practice, most bullets are not truly aerodynamically stable (center of aerodynamic pressure is not behind the center of gravity), so they wind up going unstable as soon as they go subsonic, regardless of spin. Brent ---------------------------------- www.jumpelvis.com Quote Share this post Link to post Share on other sites
JohnRich 4 #28 October 10, 2003 QuoteI believe that if something is dropped... and is allowed to fall, even at it's terminal velocity that it has the posibility of killing you. That depends entirely upon what that "something" happens to be, so such a general statement can't possibly be true. I was out in the rain yesterday, and none of those raindrops which hit me, despite having fallen for thousands of feet from the clouds, hurt me the least little bit. Yes, I know, a raindrop is not a bullet. That's my point - you can't generalize. Quoteyes, I believe that if you were struck with a penny thrown from the Empire state building that it could posibly end in death or bodily damage. I think that is highly unlikely. What do you estimate the terminal velocity of a penny to be? Give me your number, and then I'll weigh a penny, and calculate the foot-pounds of energy. QuoteHave a friend drop various caliber bullets from a height of lets say 10 feet to start onto your head and then progressively work up to say 1 story if your still able to. I'm not going to intentionally hurt myself. I've acknowledged that it would hurt like hell. I just don't see where enough energy is present that death is likely. QuoteI think a good study to look at would be those done by NASA on the debris in space and how things as minute as a grain of sand can have on inanimate materials. A grain of sand in space is traveling at thousands of miles per hour, unrestrained by wind drag. That is not comparable to what we're talking about here. Quote Share this post Link to post Share on other sites
bmcd308 0 #29 October 10, 2003 >>the question is would the bullet start to tumble when it reached the peak of its arc << If it is fired other than exactly vertical, it will in all likelihood reach the ground stable, particularly if its center of gravity is right on its axis. In actual practice, bullets tend to go unstable as they pass back through the sound barrier and tumble. That is why the useful range of a rifle for accurate fire is much less than the longest distance it can chuck a round. >>I also think getting hit in the top of the head by a small tumbling peice of metal travaling at 120mph would kill you. << It might. Brent ---------------------------------- www.jumpelvis.com Quote Share this post Link to post Share on other sites
JohnRich 4 #30 October 10, 2003 QuoteThe tumbling at 200m plus is caused by turbulence as the bullet goes subsonic. I'm aware that bullets get "unstable" when they drop below sonic speeds, but I was under the impression that just meant some wobbling was introduced, and not complete tumbling end-over-end. I have only one rifle that does that; an old 6.5mm WWII Japanese Arisaka with a shot-out barrel. The bullets actually make a whizzing noise going downrange, and produce "keyholes" in the target, with a side-profile hole of a bullet. Quote 5.56 NATO 62gr bullets destabilize quickly out of older M-16s with 1 in 12 twist barrels, because the barrels were designed for 55 gr ammo. It's obvious to me that you know something about shooting. Match shooters use even heavier bullets, 69 and 80 grains, in AR-15's, with a 1-in-7 twist rate barrel. (For the non-shooters, that means one revolution in the rifling occurs every 7 inches of barrel length.) A problem that can occur with reloaders who push their pressures too high with these fast twist barrels, is that the bullet can be spun so fast that it literally spins itself apart in mid-air, and nothing ever reaches the target. Quote Share this post Link to post Share on other sites
LouDiamond 1 #31 October 10, 2003 Ok, since some of us are of the consensus that an object, in this case bullets, can cause bodily damage when falling from the sky I think those who question it should consider is the following: 1. Are the injuries sustained penetration related? 2. Are the injuries blunt trauma related? 3. What are the probable entry points on the human body? 4. What are the forces generated by those objects striking a human body? I think there is quite a bit of difference in rain and bullets here. I hope everyone involved is in agreement on this. If you really believe a bullet falling out of the sky doesn't have the ability to kill you then I think you are fooling yourself."It's just skydiving..additional drama is not required" Some people dream about flying, I live my dream SKYMONKEY PUBLISHING Quote Share this post Link to post Share on other sites
bmcd308 0 #32 October 10, 2003 >>I'm aware that bullets get "unstable" when they drop below sonic speeds, but I was under the impression that just meant some wobbling was introduced, and not complete tumbling end-over-end. << It pretty much depends on the individual bullet. If you are shooting Federal Gold Medal Match, you'll get a little instability. If you are shooting some Portugese crap that you got for 3 cents a round delivered, it might tumble right out of the barrel. If I recall correctly, the tendency to tumble is directly related to quality control - if the center of gravity of the bullet is exactly on the long axis of the bullet and is behind the center of aeordynamic pressure (almost impossible to achieve the latter), then the bullet will stay stable. If not, it will wobble. Really bad wobbling is tumbling. >>A problem that can occur with reloaders who push their pressures too high with these fast twist barrels, is that the bullet can be spun so fast that it literally spins itself apart in mid-air, and nothing ever reaches the target. << It looks cool when it happens. You can see a little cloud of dust in the air when it comes apart. In 223, the bullets I have seen vaporize the most are actually the really light ones, since they have a really thin jacket that gives way from the scoring coming down the barrel. The longer-ogive heavy bullets are usually pretty tough, and if your buddies are blowing those up, they are really pushing the velocity. I have no experience with 6mm PPC, which is a notorious "bullet blowed up" caliber used by benchrest shooters. The really fast .17 varmint bullets have a reputation for blowing up, too, but all I can speak for is 223. Brent ---------------------------------- www.jumpelvis.com Quote Share this post Link to post Share on other sites
kallend 2,125 #33 October 10, 2003 Quote>>the question is would the bullet start to tumble when it reached the peak of its arc << If it is fired other than exactly vertical, it will in all likelihood reach the ground stable, particularly if its center of gravity is right on its axis. In actual practice, bullets tend to go unstable as they pass back through the sound barrier and tumble. That is why the useful range of a rifle for accurate fire is much less than the longest distance it can chuck a round. >>I also think getting hit in the top of the head by a small tumbling peice of metal travaling at 120mph would kill you. << It might. Brent Two tidbits of information: 1. Hoerner, the aerodynamicist who worked for Messerschmidt on the Me109 and then invented those fancy drooped wingtips for airplanes, states the subsonic drag coefficient of a bullet going nose-first is approx 0.3 (depends a little on the detailed shape). You can work out terminal velocity from this and the weight of the bullet, for this configuration. 2. Some years ago I was an expert witness for the defense for the engine maker of a top-fuel dragster that had blown its clutch. A small bolt from the clutch, no bigger than a bullet, had gone clean through the chest of a spectator and killed him. (Hence the lawsuit and need of experts). We (the engineers) estimated that the bolt was travelling at less than 200mph when it hit the guy, based on the clutch dimensions and engine rpm when it blew.... The only sure way to survive a canopy collision is not to have one. Quote Share this post Link to post Share on other sites
kallend 2,125 #34 October 10, 2003 And another tidbit. Also some years ago I was a consultant to the US Navy weapons research center in southern Indiana. They were having problems with fuzes on 5" shells (premature detonations), and so they had instrumented some shells and were firing them straight up in the air at the test range. Apparently they did turn over at apogee, and come down nose first. I think they said the shells reached about 50,000ft at apogee! It was a neat experiment - the instrumentation consisted of a microcomputer embedded in the shell that monitored the fuzing and arming mechanism. When they recovered the shell they downloaded the data for analysis.... The only sure way to survive a canopy collision is not to have one. Quote Share this post Link to post Share on other sites
bmcd308 0 #35 October 10, 2003 >>Apparently they did turn over at apogee, and come down nose first. << An artillery shell is much more likely to have its cp behind its cg and therefore turn over and fall stable. A bullet is basically a solid chunk of lead with a cone shape (sort of) out front and a cylidrical section in the back. So its cg is normally pretty far back. An artillery shell will be much more nose heavy. In previous posts, you have mentioned an interest in HPR, so I am sure you have been witness to at least a couple of recovery failures that came in stable. Same principal applies even if you don't have fins. I bet an artillery shell falling from 50K made a heck of a crater, as I can't imagine is cd being very high, and it would come down stable. Ouch. Moving on to other posts, if the real question is whether some yahoo shooting up into the air can kill you, the answer is yes, and the further from vertical the barrel is pointed when the bullet is fired, the higher the likelihood that you are going to be seriously injured. Like any gunshot wound, it's going to be a penetrating injury. While it is possible that your skull or a thick leather jacket would stop a bullet that was fired somewhere near vertical, my guess is that a hit at a couple thousand yards from a 223 (which would require a 45 degree or so angle) would still penetrate normal clothing and cause serious injury. While I do not believe that one fired exactly along a line drawn from the shooting position to the center of gravity of the earth would kill you, I'm not confident enough of that to run around trying to catch one. Certainly, even a barely moving bullet that got into your eye socket would do serious and possibly lethal damage. My advice to you would be NOT to hang out downrange from a firing position. Brent ---------------------------------- www.jumpelvis.com Quote Share this post Link to post Share on other sites
JohnRich 4 #36 October 10, 2003 Quote1. Are the injuries sustained penetration related? 2. Are the injuries blunt trauma related? It could be either, or both, depending upon the weight and shape of the bullet. A spire point bullet might tend to penetrate, while a blunt nose .45 probably would not. Quote3. What are the probable entry points on the human body? For our discussion of bullets fired straight up: the top of the shoulders and the top of the skull. And maybe your toes, belly or ass, depending upon how far they stick out... Quote4. What are the forces generated by those objects striking a human body? The below referenced web site is one of many that contains a calculator for determining foot-pounds of energy. Using that calculator, with a 115-grain 9 mm bullet, falling at 100 mph (~150 feet per second), gives only 6 ft-lbs of energy. That's not much. The Army considers that it takes 60 ft-lbs to produce a "disabling" injury. http://www.pyramydair.com/site/articles/formulas/ QuoteIf you really believe a bullet falling out of the sky doesn't have the ability to kill you then I think you are fooling yourself. I think it *might* have the ability, but that the probability is very low. Sort of like a BB gun. People have been killed with BB's fired from low velocity air guns, but it is very rare. If a freefalling bullet hit a baby on the head, where the baby's skull hasn't grown together yet, that might certainly be fatal. But for adults, I don't think so. Quote Share this post Link to post Share on other sites
JohnRich 4 #37 October 10, 2003 Here is a photo of the four types of bullets used in my experiment, with a dime coin for scale. From left-to-right, they are: 1) .22 rimfire 25-grain 2) .223 55-grain 3) 9mm 115-grain 4) .45 230-grain The .22 rimfire is slightly mangled, as the bullet-pullers I have in my reloading equipment don't handle that one. There are 437.5 grains to an ounce, so even the biggest, heaviest of these bullets, is barely more than a half-ounce in weight. Quote Share this post Link to post Share on other sites
JohnRich 4 #38 October 10, 2003 Quotea top-fuel dragster that had blown its clutch. A small bolt from the clutch, no bigger than a bullet, had gone clean through the chest of a spectator and killed him. We estimated that the bolt was travelling at less than 200mph when it hit the guy That would have to be an awful tiny bolt. Let's not mistake the size of a "bullet", with the size of a "cartridge". This is a common mistake made by non-shooters, who use the terminology incorrectly. A .30-06 cartridge, loaded, is about 3.2" long, to include the brass case plus the bullet. This is the size of a bolt as I think of bolts used in car engines. The .30-06 bullet, on the other hand, just the projectile by itself, is only about 1.1" long. A bolt would also be made of hard steel rather than soft lead, and thereby penetrate flesh easier and deeper, like an armor-piercing bullet. So the characteristics aren't the same. A hard steel bolt at 200 mph, is not a soft lead bullet at 100 mph. That may be the difference between a fatal injury, and a minor injury. Quote Share this post Link to post Share on other sites
JohnRich 4 #39 October 10, 2003 Quote 5" shells (premature detonations), and so they had instrumented some shells and were firing them straight up in the air at the test range. Some people get to have all the fun... I guess they had a really deep bunker to hide in while waiting for these to fall back to earth. It must have taken many minutes. .30-06 bullets fired from a machine gun, as reported by Hatcher, take from 1 to 1.5 minutes to fall back to earth. Quote Share this post Link to post Share on other sites
mnischalke 0 #40 October 10, 2003 Hey, I started thinking about sectional density, ballistic coefficient and stuff like that and something came to me. I think I want do some freefall testing too. I got the perfect subject too: Lawn Darts They're fin stabilized--cg is far forward. Anybody know where I can get some? mike Girls only want boyfriends who have great skills--You know, like nunchuk skills, bow-hunting skills, computer-hacking skills. Quote Share this post Link to post Share on other sites
Zenister 0 #41 October 10, 2003 QuoteQuoteWere the tests all done with #s or did they use cadavers? There have been Army studies of wound ballistics using live animals. Thousands of them. Yech. That's where those wound energy numbers come from. You can readily calculate the energy, in foot-pounds, of a fired bullet using the factors of mass and velocity. And then compare that to the results of those wound studies. I'm sure today's animal rights activists would have a fit over those studies... they use a gel block now that has the same density and resistance to penetration as a human body. Last time I was at the range with my father they had some out there for the new sherrif trainees to see the effects from various rounds. I'm not sure how expensive they are, but it wouldnt be to hard to do the 'drop' experiement from various heights until it began to penetrate. QuoteBut did the bullet impact straight down, or at an angle? If it travelled in an arc through the sky, it would retain much more velocity, than a bullet which freefalls back to earth, having expended all of it's muzzle velocity straight up. Since you didn't indicate that you heard the round being fired, that would tend to suggest that it was fired from some distance away, and thus was not a vertically-oriented shot. So that particular shot may have had more retained energy than the straight-up firings were discussing. no it appeared to be at a slight angle as i recall and hit with enough force to penetrate the skin of the hood but not pass thru...(i may be able to get the insurance photos from her to post) we didnt here any shots fired, but of course we were also driving and it hit the hood within a second or so of us pulling in. (my door was closed but she had not shut hers yet.)____________________________________ Those who fail to learn from the past are simply Doomed. Quote Share this post Link to post Share on other sites
Zenister 0 #42 October 10, 2003 QuoteHey, I started thinking about sectional density, ballistic coefficient and stuff like that and something came to me. I think I want do some freefall testing too. I got the perfect subject too: Lawn Darts They're fin stabilized--cg is far forward. Anybody know where I can get some? i have 3/4 of a set still ____________________________________ Those who fail to learn from the past are simply Doomed. Quote Share this post Link to post Share on other sites
mnischalke 0 #43 October 10, 2003 I am getting the feeling those things are worth their weight in gold... ballistic gelatin sucks ass to make, but it's reuseable and if you keep it cold, it lasts quite a while. fun shit to play with. Now, as soon as I can get federal to sell me some hydrashock 124g bullets, I can make up some good rounds for my .38 super. I'd like to see what kind of a difference there is between hydrashock and corbon factory loads. Sorry to wander off topic. It's been a long week mike Girls only want boyfriends who have great skills--You know, like nunchuk skills, bow-hunting skills, computer-hacking skills. Quote Share this post Link to post Share on other sites
Hooknswoop 19 #44 December 15, 2003 "In northern Kirkuk, eight people were killed and 80 wounded by shots fired in the air during celebrations of the capture, said hospital official Shehab Ahmed." Derek Quote Share this post Link to post Share on other sites
Kennedy 0 #45 December 15, 2003 I've heard of well planned ambushes that didn't result in so many casualties. Are we sure one or two weren't firing into the crowd rather than the sky?witty subliminal message Guard your honor, let your reputation fall where it will, and outlast the bastards. 1* Quote Share this post Link to post Share on other sites
cvfd1399 0 #46 December 15, 2003 The only thing I think I can add to this is that the bullet spins at an average of 90,000rpm , I would think after it arcs out and turns towards earth that it would loose that spin. Also after some small bullets such as the .223 it will start to tumble after loosing a certain amount of speed to keep it stabilized. That is the effectiveness of the small .223 is to tumble through a person. Quote Share this post Link to post Share on other sites
pilotdave 0 #47 December 15, 2003 Spinning that fast, do the bullets even flip over at the tops of their arcs? Could be coming down backwards.... Dave Quote Share this post Link to post Share on other sites
newsstand 0 #48 December 15, 2003 There are really two different things going on here. What happens if the bullet goes straight up and straight down. A quick Google search talks about the penny and it not being likely to kill, although a pointy object might be different. http://www.urbanlegends.com/science/penny_falling_impact.html (yes I know this says in a vaccuum). The other is if it comes down at an angle which JohnRich says pretty early on is a different matter. Even if the person fires the first shot straight up recoil is going to move their hand and additional shots are going to be at various angles. If you have ever seen coverage of this remember that these folks tend to be using automatics with one hand, not a stable shooting platform. "Truth is tough. It will not break, like a bubble, at a touch; nay, you may kick it about all day like a football, and it will be round and full at evening." -- Oliver Wendell Holmes Quote Share this post Link to post Share on other sites
Kennedy 0 #49 December 15, 2003 The .223 also has a tendency to tumble because it crosses the sound barrier in flight. When it does this (goes transonic) something forces bullets to tumble. This happen in other calibers as well. I think it happened to both .50 AE and .50 bmg, so weight and length versus width do not prevent this. The solution is to keep round below the speed of sound, or to keep the round above it, until they find a target. FYI - the .50 AE is a handgun round for the Desert Eagle, the 50 bmg is a rifle round for Browning Machine Guns and .50cal rifles in service today, such as Barrett Rifles.witty subliminal message Guard your honor, let your reputation fall where it will, and outlast the bastards. 1* Quote Share this post Link to post Share on other sites
kallend 2,125 #50 December 15, 2003 QuoteThe .223 also has a tendency to tumble because it crosses the sound barrier in flight. When it does this (goes transonic) something forces bullets to tumble. This happen in other calibers as well. I think it happened to both .50 AE and .50 bmg, so weight and length versus width do not prevent this. The solution is to keep round below the speed of sound, or to keep the round above it, until they find a target. FYI - the .50 AE is a handgun round for the Desert Eagle, the 50 bmg is a rifle round for Browning Machine Guns and .50cal rifles in service today, such as Barrett Rifles. Assymetric vortex shedding and/or transsonic shocks from the nose of the bullet would cause tumbling. Almost impossible to do anything about it without active control. Spin stabilization will cause the bullet to precess, which won't help much either. It's a problem with missiles too, the Air Force has a research program on active control.... The only sure way to survive a canopy collision is not to have one. Quote Share this post Link to post Share on other sites
