Bullets fired in the air

A: This question is hard to answer in general. The best I can give is a "worst-case" estimation.
When a gun is fired vertically, the bullet after some time reaches a summit where the velocity is zero, and then falls back. The bullet will fall back base first which is hard to calculate. I can estimate the velocity if it would fall nose first, that is the normal flying position for which drag is well known - so the real terminal velocity will actually be smaller than the following prediction.

• For a .22 lr bullet (m=40 grain, v0 = 1150 ft/s)
  the summit will be at 1164 ft, the total flight time 30 seconds and the terminal velocity 270 ft/s

• For a SS109 military bullet (m= 55 grain, v0=3200 ft/s)
  the summit will be at 2650 ft, the total flight time 44 seconds and the terminal velocity 404 ft/s.
  For this bullet are indications that it will become unstable. This will further reduce summit height and terminal velocity considerably.

http://www.nennstiel-ruprecht.de/bullfly/faq.htm#Q13

You wrote:The bullet will fall back base first

Why? and how did you come to this conclusion?

Wangito.

Rakesh, I'm afraid you are wrong. Any bullet fired perfectly vertically into the air will INITIALLY fall back butt first, but aerodynamics being what they are the bullet will flip end for end and settle into a nose down attitude. But 99.999% of the time, the bullet will not be perfectly vertical, therefore it will be on a parabolic arc and will probably remain moving forward throughout it's travel. Most bullets are designed for minimum aerodynamic drag when travelling nose first, therefore, yes they will reach terminal velocity at some point, but that velocity can be very very high. high enough to kill someone if it strikes them in the right place.

Hi Rorschach,

Any bullet fired perfectly vertically into the air will INITIALLY fall back butt first, but aerodynamics being what they are the bullet will flip end for end and settle into a nose down attitude.

Your description doesn't align with the attitude of falling bullet shaped objects

What kind of aerodynamic principle are you describing? That of and arrow shot straight up? Will initially fall shaft and feathers first then the weight of the arrow head will change the orientation towards Terra. But that's gravity not aerodynamics.

Now I could be wrong, but I'm assuming that the back end of the bullet is blunt and not terribly aerodynamic, spitzer or boat tail bullets will probably change the outcome. The buffeting of turbulent air pushed ahead of the blunt end, combined with the residual spin imparted from the rifiling should begin the bullet to precess/tumble. Once the bullet begins to move away from vertical then the drag on the larger crosssection of the back end will slow the back end more than the smaller crossection of the pointed end. This should lead to the bullet flipping end for end and eventually settling in a point down attitude if it falls far enough. I will also admit that the CG of the bullet can and will affect that. if the CG is too far back toward the base of the bullet, the bullet will have the propensity to tumble, even in level flight, much like your arrow analogy. In fact the .223 bullet used in 7.62 NATO rounds do have that propensity (it is my understanding that this is true of many military bullet designs and is done intentionally so that the wound channels they create are large and they do not overpenetrate or punch all the way through without imparting a significant amount of their energy into the target.). MOST bullets have their CG far enough forward that tumbling is not an issue. But in the case of military ammunition, accuracy is not a high priority.

I'm not certain this talk of perfectly vertical is worthy of disputation in a practical (other than theoretical) sense...because Earth rotation as well as Coriolis force deflection and (rifled) projectile spin are almost certain to keep the bullet on a "forward" trajectory.

Incidentally, last Saturday a movie, Six Days Seven Nights starring Harrison Ford and (leading lady) was broadcast on a local channel. It was a high (romantic) comedy adventure in which, after foiling and escaping an evil pirate landing party on an uninhabited island, Ford and his companion were attempting to escape the island in Ford's plane, to which the two had rigged pontoons removed from a crashed WWII plane on the island. The harrowing lift-off occurred just in the nick of time as the pirate ship closed in, but not in time for Ford to steer away from a take-off path leading directly over the ship. In the meantime, the head, most ferocious and naughty pirate had taken over the manning of a high caliber gun, intent on shooting down the plane and its occupants. With steely (Ford style) abandon, Ford kept on course over the plane while the pirate chief continue his salvo, swinging the gun muzzle further and further upward towards vertical. Finally, after the last shot (the gun could be pitched no further), and hearing no report of a hit, it suddenly but only belatedly dawned on our ruthlessly stupid pirates...that there was time only to swear, but not jump into the drink, before their seaborne home was blown to smithereens.

So, yes, shooting at the sky can be a "dangerous" thing.

yes.

Depends on the weight of bullet. Weight equals energy. Like a cat in a hail storm--the larger the hail-- the louder the MEEOW.

People are injured by bullets fired into the air almost every year in the Houston Texas area, particularly on New Years...

It's been covered here--http://cr4.globalspec.com/thread/23432#comment247218

4th of July question this year.

Thanks Kilgore, I appreciate the reference, I guess my question was, would it be more likely to kill them or leave a slight bruise.

Thankfully, you have to have a very good reason to own a gun in Australia.

Tony

It can kill. As Del said. It is especially likely if it falls into your head. When I lived in Manhattan a woman was killed by a bullet fired off a roof in Harlem on the otherside of Central Park. I believe it was identified as a nine millimeter bullet. (I could be wrong, but they are common.) Sometimes people are killed by falling air conditioners in New York City. I knew someone who knew a guy who got decapitated by a helicopter rotor blade. It is irresponsible for anyone to fire a gun like it was some sort of harmless fireworks. Fireworks aren't harmless either. Everytime I shoot at something, I at least have a target.

There is a new law in the US, wherein, if you fire a handgun, or rifle round into the air, and it comes down, and kills someone, you can be tried for the action. The question is...how can the authorities tell exactly which handgun/rifle fired the projectile, and further, from where? I'm in Arizona, where everybody has a weapon of some sort, capable of killing a person. If they do indeed, fire a round into the air, and it comes down and kills someone...well, good luck to the prosecutors in search of a conviction.

I understand every gun has a unique "signature" caused by the rifling. Is it possible to fire each gun, before it is sold and record that signature on a database or does the signature change significantly over time?

Tony

Nope, rifling changes as the weapon is used. Corrosion, wear, fouling all play a role in the "evolution" of the bore. So no, that is a fool's errand. Two bullets fired within weeks of each other (assuming the gun was not left in salt water or something like that) can be compared, but not bullet #1 and bullet #2000. Besides, can you imagine how much data that would be? And how do you write a search routine to compare hundreds of thousands (or millions) of images?

This is not a new law. It has ALWAYS been illegal to negligently kill someone. The trick is proving who did it.

Just by coincidence, I saw a Myth Busters episode yesterday dealing with just that subject. It turns out that if the gun is fired very close to vertically, the bullet will tumble on the way back down and not achieve enough velocity (about 100 mph) to be fatal. However, if it is fired at a small angle from vertical (as would be likely), it follows a parabolic trajectory coming down pointy end first, which could very well be fatal.

They tested this on "Mythbusters"

If the firearm is fired perfectly vertical, then the bullet will tumble during its return to earth and will reach Terminal Velocity. It will hurt, but not likely kill you.

However, if the firearm is fired at an angle, then the bullet will retain its Kinetic Energy (less frictional losses) and can very easily Kill anyone in its path.

They did this experiment on "myth busters". they fired a 9mm and a 30-06. the terminal velocity on the way down was almost exactly the same for both bullets. around 150 ft/sec. they experimented with a pigs head and found that although it might hurt it would not kill You, however they interviewed a doctor who specializes in this type of injury and found that a few people were acctualy killed from bullets being fired into the air.

oilcan13

Bullet fire exactly straight up and falling straight down not lethal. However almost impossible to fire staright up. Fired at any other angle bullet will retain horizontal velocity component making it lethal.

I couldnt begin to tell you how much terminal velocity a bullet would need to kill a human, but I think its pretty safe to say the likelyhood of a .22 cal steel bullet killing a person in the way you described is far less then say a 30 mm depleated uranium round. Shotgun "shot" will simply bounce off of you.

The Mythbusters addressed this theory pretty definatively. Here's a link to their video:

http://videos.howstuffworks.com/discovery/6547-mythbusters-bullets-fired-up-uncut-video.htm

Rifle/pistol bullets are spin stabilized. The myth busters show used paint ball guns which are not spin stabilized-at least not the gun they used. Nothing was learned because of that simple difference. A properly spin stabilized bullet does not flip over or tumble. Every gun barrel/bullet configuration will have its own amount of stabilization. Anyone who ignores this is just getting bad information in their results.

I can't speak to any other bullets but I have seen a single bullet fired nearly straight up from a 50bmg that landed on its butt. It was not tumbling when it hit because it stuck a sandwich before it hit the ground. It made a perfectly round wadcutter type hole before sticking in the dirt. A tumbling bullet would not make a perfectly round hole. This was at U-tapao Thailand in early 1970. I still have the bullet. It was not my sandwich.

Over stabilized bullets when fired in a high arc tumble also loosing velocity.

The M-16 used the overstabalized design so the bullets arc of trajectory was normal but the bullet itself kept the orientation of the angle of the barrel when fired. This caused the bullet to hit at an angle to its trajectory. This is where the misconception of it having a tumbling bullet came from. The off angle impact caused the round to make nasty wounds.

Brad

dear sirs

as a theory of projectile in vaccume the firing velocity and its starting elevation with respect to horizone is equale to th falling velocity and elevation if both in the same elevationregardless the shape of projectile and mass.

but in real firing that is not the same because alot of external sffect applied to the projectilesuch us ( air dencity,projectile shape, projectile spin around the tragectory line,the hight from sea leveloutdoor temprature,and the center of gravity.all these effects apply what its called (DRAG FORCES) which eleminate the speed and tragectory of the projectile.

Each effect has its independant factores but all projectile designer can not tell the exact factor for each effect . because it cannot be calculated exactly ,and all designer depend on previouse ammunation caracterstics and modify a new one .

so in general way the desiogner assume that the exact falling speed to the ground at the same firing level is about 605-70% of the initial speed so if firing velocity is 1000 m/sec the falling speed will be at least 600 m/sec and this speed is very leathal for humen body . and if it hit any body accedantly it will injure him or even kill him if it his sensative portion of his body like(head or heart) >

according to that any bullet fired at any angle will fall on ground with lethat power , and it is happend in many places in the world and reported officially that in som un amed shootings some body killed or injuered harmfully.from that it must be to issue some low to forbiden shoot aimlessly in the air because there is a chance to kill some inoccent boby.

It does happen from time to time, resulting in serious injury or death. As I've heard, it's not inconceivable for a bullet to reach muzzle velocity or very close upon return.

Shooting guns into the air could also land one with a battery or manslaughter charge, it the bullet finds someone.

I am not sure if this is helpful but with large caliber weapons, I am thinking battleship guns, hyperbolic fire use to be the best way to penetrate another battleships armour.

Rather than the projectile slowing down as it gets closer to the target, as in a howitzer shot. The hyperbolic shot is actually accelerating due to gravity. There are limitations to this due to aerodynamics.

It was exactly this form of fire that the German battleship Bismark used to sink HMS Hood. http://en.wikipedia.org/wiki/Bismarck_(battleship)

"At 05:54 the range was down to 22,000 yards (20 km), at 05:57 it was down to just 19,000 yards (17 km). Bismarck then fired a fourth salvo which was slightly long and astern of Hood. At the same time Holland had ordered " 2 Blue", a 20 degree turn to port. Before the ship began a turn to port Hood fired a fifth salvo at 05:59:30.^[14]

At 06:00 Hood, which was in the process of turning to port^[15] to bring her full weight of armament to bear on Bismarck, was hit amidships by at least one shell from Bismarck's fifth salvo at a distance of under nine miles (16,500 yards). Very shortly afterwards observers on both sides saw a huge jet of flame race skywards, followed by a rumbling explosion that split the huge ship in two. Splinters rained down on Prince of Wales, 400 yards away. Hood's stern rose and sank shortly before the bow, all within three minutes. Admiral Holland and 1,415 crewmen went down with the ship. Only three men (Ted Briggs, Bob Tilburn, and Bill Dundas) survived."

Extract from Wikipedia.

You can bet that the three survivors were not in the engineering division.

Remember 1/2MV², The mass is important but the speed is what counts. So if the projectile is gaining speed, then being in close proximity to Ground Zero is less than desirable.

BAB

Volume is a cube function, drag is proportional to the frontal area( a square function). This is changed by the coefficient of drag, but holds true for similar profiled projectiles of different masses. A projectile from a 10" gun may well have a higher terminal velocity than a .303 bullet, and may well accelerate from the peak height of the path as it descends. A bullet slows to a terminal velocity as the path tends towards vertical with drag. The Hood and several other British battleships had design flaws in the ammunition stores that allowed flash to propagate and ignite the propellant stores. A flash in this case is not light, but is an overpressure of hot gasses to several atmospheres that enters the propellant stores via badly made flash blockers or badly trained crews. German ships had very strong propellant stores and well designed flash prevention systems and were very hard indeed to sink. Inquiries blamed several people after the hood sunk, but blame was deflected by influential people .

hello everyone,

i have an experience from being in the military that is close to this topic.

i was in artillery. fire direction control. telling the guns where to point and what elevation of the guns.

we were fireing 155mm long toms (extended barrel). we were testing the new "swiss rammers" together with the new "extended barrel.

before we get the job to do extended testing (50,000 rounds), the equipment was first tested at aberden proving grounds to give us base line data, on what they thought would be happening.

well, now to reality: everything worked fine until we got to "high angle testing" as we approached extreme high angle, we lost a round. normaly once the gun is angled above 45 degrees, the impact point starts walking back towards you. so, that theoreticly you can loft a round that will land fairly close. in the real world this translates to still a minimum of 2,000 to 3,000 feet, which is actually really close.

well, we were doing fine until really high angle. then we had a range "check fire". a round had left the impact area. it had landed within 150 of a group of students sitting in bleachers. i plotted the impact point, and realised that it was on our gun target line and informed the exo (range safety officer standing next to me, that if our round went long, it could be us). he was not pleased, but reported this to the range safety officials. turned out it was us. the round at extreme high angle had become unstable, tumbled and because of the dynamics, went long instead of short. the round did not explode. they dug a well next to the impact point, exposing the round so as to remove it. found that the round was buryied butt first into the ground.

so, yes, coming down butt first is what happens in the real world to an unstable round.

In researching the concept of overstabilization (which I had never heard of up to this point.) I ran across this post that might be educational:

Barrel Twist Rate and Bullet Stability

Twist Rate

Bullet stability depends primarily on gyroscopic forces, the spin around the longitudinal axis of the bullet imparted by the twist of the rifling. Once the spinning bullet is pointed in the direction the shooter wants, it tends to travel in a straight line until it is influenced by outside forces such as gravity, wind and impact with the target.

Rifling is the spiral or helix grooves inside the barrel of a rifle or handgun. These grooves were invented a long time ago, perhaps as early as the 14th century. However, the smooth bore, using the round ball, was the choice of weapons for warfare even through the American Revolutionary war. The smooth bore musket could be loaded faster than the rifle and didn't foul, as bad, with the combustion products of black powder.

The rifling grooves helix is expressed in a twist rate or number of complete revolutions the grooves make in one inch of barrel length. A 1in10 or 1:10 would be one complete turn in 10 inches of barrel length.

How important is twist rate? David Tubb, a winner of several NRA High Power Rifle Championships, was using a .243 rifle with a 1 in 8.5 twist barrel. He wasn't able to get consistent accuracy until he changed to a rifle barrel with a 1 in 8 twist. The ½" twist change made all the difference between winning or losing the match.

A term we often hear is "overstabilization" of the bullet. This doesn't happen. Either a bullet is stable or it isn't. Too little twist will not stabilize the bullet, while too much twist, with a couple of exceptions, does little harm. Faster than optimum twists tend to exaggerate errors in bullet concentricity and may cause wobble. The faster twist also causes the bullet to spin at higher rpm, which can cause bullet blowup or disintegration because of the high centrifugal forces generated. For example, the .220 Swift, at 4,000 fps., spins the 50-grain bullet at 240,000 rpm.

One of the first persons to try to develop a formula for calculating the correct rate of twist for firearms, was George Greenhill, a mathematics lecturer at Emanuel College in Cambridge, England. His formula is based on the rule that the twist required in calibers equals 150 divided by the length of the bullet in calibers. This can be simplified to:
Twist = 150 X D2/L
Where:
D = bullet diameter in inches
L= bullet length in inches
150 = a constant

This formula had limitations, but worked well up to and in the vicinity of about 1,800 f.p.s. For higher velocities most ballistic experts suggest substituting 180 for 150 in the formula. The twist formulas used in the Load From a Disk program, featured at this web site, uses a modified Greenhill formula in which the "150" constant is replaced by a series of equations that allow corrections for muzzle velocity from 1,100 to 4,000 fps.

The Greenhill formula is simple and easy to apply and gives a useful approximation to the desired twist. The Greenhill formula was based on a bullet with a specific gravity of 10.9, which is about right for the jacketed lead core bullet. Notice that bullet weight does not directly enter into the equation. For a given caliber, the heavier the bullet the longer the bullet will be. So bullet weight affects bullet length and bullet length is used in the formula.

To measure the twist of a barrel, use a cleaning rod and a tight patch. Start the patch down the barrel and mark the rod at the muzzle. Push in the rod slowly until it has made one revolution, and then make a second mark on the rod at the muzzle. The distance between marks is the twist of your barrel.

To see how this works out, assume you bought a .222 Remington rifle and you measured the twist rate as described above. The twist was 1 in 14. You have two .224 bullets you want to use, the 70-grain Speer SPS and the 50-grain Hornady SX. The Speer bullet measures .812 inches in length and the Hornady measures .520 inches. Using the formula above we calculate the following twist rate:
Speer 70-grain: 1 in 9
Hornady 50-grain: 1 in 14

These calculations show that the 50-grain bullet will be stabilized, but the 70-grain won't. Sure enough, when you try these bullets out, the 50-grain shoots ¾ MOA while the 70-grain won't group on the paper at 50 yards.

Interesting! I learned it from a range master in the US army when he was explaining why my Kentucky windage shots left a oblong hole from a .223. He is also the one who told me it didn't tumble but struck off axis to the trajectory, the axis of the bullet still aligned with the barrel. It matched the target data. My observation was the M16 was an accurate piece of junk. (it only had to see sand to jam) Heard it is much improved now but I'd take the 243.

Brad