Don't know if you guys have seen the Mythbusters episode where they tested out the valocity of a falling bullet and to see if it can do any serious damage. A potential real life case may have occured in Macau, Southern China 2 days ago where an officer fired his .38 reolver up in the air 5 times to stop crowds from advancing in a protest (above him was a bridge in close proximity). A dude 300 meters away (beyond a small hill), stopping at a junction on a scooter was hit at the back of the neck. He had to undergo an operation to remove the bullet. Initial report shows he was hit by a .38 bullet that fell from the sky but no ballistic report as yet to prove the bullet was fired from the officer's reolver. If that is proven, the myth can truely be confirmed

If it landed 300 meters away it was not fired in a perfect vertical. The Episode concluded that unless the gun was perfectly vertical, the bullet would not go straight up and free fall but travel in a ballistic arc and still be leathal.

That show had a very flawed methodology.

First, a human skull is nowhere near as tough as a pig's skull, so "saying that if a bullet won't penetrate a pig's skull, it won't penetrate a human skull" is utter nonsense.

Second, their homemade windtunnel couldn't have produced accurate terminal velocity data for several reasons, the square cross-section guaranteed that the windspeed profile wouldn't be consistent, the turbulent airflow would be impossible to measure accurately even if the windspeed meter used had been placed correctly (which is wasn't), and third the bullets weren't spinning, so they tumbled as they "fell", which reduced their ballistic coefficient and thereby their terminal velocity.

Many others have done independent calculations of what a falling bullet's terminal velocity should be (I've done that calculation myself), and the answer that we all come up with, independently, is between 250fps and 300fps.

The show's "wind tunnel" came up with 150fps.

They interviewed a doctor who researches falling-bullet injuries and he displayed an x-ray of the head of a falling-bullet victim who died from injuries to the head. The bullet penetrated his skull and came to rest on the bottom of the cranium after transiting the brain. That's pretty conclusive, right there.

The whole "safe if it's fired straight up" nonsense was an attempt to reconcile the bad windtunnel/pig's head data with the actual accounts of people getting hurt/killed by a falling bullet, but even that didn't make a whole lot of sense, as the bullets they fired "straight up", using a carpenter's level as a vertical reference (and who's going to use one of those when he's drunk and firing up in the air?) fell to earth some 100 yards away, minimum. They never found where the rifle bullets landed.

The forces generated by a large-caliber bullet when it hits the top of someone's head can exceed a ton. The pressures are astronomical, and the likelihood of the bullet merely bouncing off the scalp nonexistent.

Firing a gun into the air is playing Russian Roulette with someone else's life. I can hardly think of anything more irresponsible than that.

A falling bullet can do serious damage if it follows is ballistic trajectory. If a bullet was fired straight up and fell to the ground it would not be deadly because it will only fall at its maximum velocity. Which has been proven that a bullet's maximum velocity is not deadly when falling after being shot straight up.

[quote]Which has been proven that a bullet's maximum velocity is not deadly when falling after being shot straight up.[/quote]

No, all they "proved" was that a falling bullet won't kill a pig.

we were anchored up in a flat calm bay shooting our guns straight up. we actually managed to get the bullets to land on the boat. they didn't even mark the wood hatch covers.they just bounced off.i doubt they would be lethal

[quote]they didn't even mark the wood hatch covers.they just bounced off.i doubt they would be lethal[/quote]

Do the math, and you'll understand why there's a difference between a wood deck and a person's skull.

The myth was in my view thoroughly busted.. A bullet that falls straight down does not have nor the mass or the velocity to kill.

Those instances where people has been killed or hurt by falling bullets, has been instances where the gunman has fired at an angle, thereby creating a ballistic trajectory.

[quote]has been instances where the gunman has fired at an angle, thereby creating a ballistic trajectory.[/quote]

That was the handwave argument they came up to try to reconcile the bad data they collected with the actual accounts of people who've been killed.

Even when they fired straight up, the bullets came down over 100 yards away. If, in real life, someone fired a gun in the air and the bullet killed someone 100 yards away, they'd be saying that the gun wasn't aimed straight up, so it came down "in a ballistic trajectory".

Newsflash: They all come down in ballistic trajectories. The odds of a bullet coming straight back down close to where the gun was, after climbing to 4000 feet in the air, are very slim. Even handgun bullets end up spending about 30 seconds in the air so any slight breeze anywhere along that trajectory will carry that bullet far enough away that they could claim it wasn't fired straight up.

It is possible to survive a falling bullet impact, depending on the caliber of the bullet, but is that really the same thing as saying it's safe to fire a gun straight up? What caliber bullet won't kill anybody under any circumstances?

Doesn't matter

in my view the myth was busted.. Bullets fired straight up does not kill.. But bullets fired at an angle does.

Bullets fired at an angle does have a bigger speed than bullets fired straight up..

It's pure physics,dearie

[quote]Bullets fired at an angle does have a bigger speed than bullets fired straight up..

It's pure physics,dearie[/quote]

When this topic came up before, I contributed the physics backing up my position.

You haven't done any calculations on this, so don't claim that you have physics on your side. You don't.

My calculations are available here, just do a Find and they should show up.

In the meantime, I'd be very interested in seeing the physics that backs up your claims, Dearie.

A bullet that falls straight down can never get anymore than terminal speed..

Do you remember the coin myth-experiment? If a coin at terminal speed could kill or hurt, wouldn't you think that a hand would fare much worse than it did by being hit by a coin at terminal speed?

The same applies with a bullet at terminal speed. Especially when you think that the mass of a dropped bullet simply isn't enough to kill. (you would have to have a .50cal sniper bullet in that case, those bullets are pure heavyweights)

Bullets that travel in a ballistic trajectory always travels at speed (They only loose speed due to friction against air, due to inertia), while a bullet that gets fired straight up will loose all speed at one point and THEN fall down, untill it reaches terminal speed (the maximum speed any object can fall in freefall.. wether it is a feather, a block of lead, a human being or a bullet)

And since it was proven that any object dropped at terminal speed can only be deadly if the mass is great enough, then it should be very easy to tell that an ordinary bullet wether it be a bullet from a rifle, an ordinary gun or revolver won't simply have the kinetic energy enough to penetrate the human skull or penetrate human skin.

But ofcourse; it does no invalidate the warnings about not firing a weapon unless you intend to kill someone or something with it.

How about letting this one rest. There are enough laws that have defecated on our 2nd Amendment rights. Maybe there is a reason why they came to that conclusion.

A .44mag bullet can weigh 240gr. That's about 1/2oz.

Assuming a Cd of about 0.3, which is reasonable, its terminal velocity will be about 300fps.

If that bullet hits someone on the top of the head, it has to decelerate to zero before it penetrates the scalp, or whatever energy is left will be imparted to the skull which is very fragile. The scalp is about 1/4inch thick.

A bullet (or anything else) decelerating from 300fps to zero fps in 1/4inch decelerates at 67500 g's. That means that 1/2oz bullet exerts an average of 2109 pounds of force over that 1/4inch to stop.

Do you suppose that a human skull can sustain 2109 pounds of force without shattering?

The pressure under the bullet, assuming, optimistically, that it's spread evenly over its entire cross-sectional area, would be 2109 pounds/(pi*(.22)^2)sq.in., or 13,872psi.

Do those numbers sound survivable to anyone here?

If the bullet landed point down, maybe not..

But do you remember that all the bullets that the mythbusters fired never landed point down? They never made a perfect circular impression where they landed, instead they made an oblong impression.. The bullets landed askew..

That caused the bullets to loose the kinetic energy faster, and also not too burrow themselves as deep as they could've had they landed point down..

Besides... The human skull, and any other bone can withstand more pressurepound per inch than anyone can imagine.. It all depends on how small or big area the pressure is spread on.

Carter, I think that one of the factors that you haven't taken into account is that the MBs demonstrated rather clearly is that bullet fired close enough to the vertical to come to a stop do not then fall back in their optimum aerodynamic orientation, but with their long axes parallel to the ground. This would greatly raise their drag coefficient-I suspect considerably higher than .3 especially since they appeared to roll and yaw around the long axis. The balloon drop rig seemed to fairly well confirm their velocity measurements. As for not finding the rifle bullets fired straight up-Ever hear of a Metal Detector, Guys?

what if, like me, you have an incredibly thick skull?

carter before you try to disprove MBs you should pay a little more attention to it as dickfez stated [quote]you haven't taken into account is that the MBs demonstrated rather clearly is that bullet fired close enough to the vertical to come to a stop do not then fall back in their optimum aerodynamic orientation, but with their long axes parallel to the ground. This would greatly raise their drag coefficient[quote]

it doesn't matter what wind shifts the bullet from a straight flight unless that wind can cause the bullet to spin on its decent it does not change the outcome of the test so when you find a naturally occuring wind capable of that then come back and prove your theory until then its a mute point the wind may affect where it lands but not its velocity on its way down

[quote]the MBs demonstrated rather clearly is that bullet fired close enough to the vertical to come to a stop do not then fall back in their optimum aerodynamic orientation, but with their long axes parallel to the ground. This would greatly raise their drag coefficient-I suspect considerably higher than .3 especially since they appeared to roll and yaw around the long axis.[/quote]

A 240gr. .44mag bullet is about the same length as its diameter. Draw a 1/2" circle, and no matter which way you put it down, you can fit it inside the circle. It's a bit more aerodynamic pointy-end first, but regardless of which way you'd look at it, you'd approximate its Cd at about 0.3, give or take. Even blunt-end first, with the cone at the end, it's still about 0.3, so that isn't a bad estimate.

As for the balloon-drop "confirming" their estimates, that balloon-drop actually proves my case that the 150fps number Adam "measured" with his windtunnel was wrong. As something falls, it accelerates at first at 9.8m/s^2, but as it picks up speed, the wind resistance slows its acceleration. When it's going half its terminal velocity, it's only accelerating at 3/4ths the acceleration of gravity, with wind resistance reducing its effective weight by 1/4th. If you drop it from the 450foot height that Adam calculated was necessary for gravity to accelerate it to the 150fps, if 150fps was its terminal velocity, it wouldn't get close to 150fps, it'd be going about half that speed due to the net effect of wind resistance slowing its acceleration.

Ask any skydiver how far it takes to fall before you get up to terminal velocity, he won't say 450 feet.

Incidentally, a human's terminal velocity is close to 200fps. According to Adam's calculations, a human falls faster than a bullet. Does that sound right to you?

Aside from doing these calculations, here, I first took a look at the falling-bullet thing with a 1500-line computer model I wrote for the USAF, capable of modeling the flight dynamics of a maneuvering reentry vehicle into the earth's atmosphere, from 300,000feet altitude and Mach 20 velocity down to ground level. It incorporated the different atmospheric densities found at different altitudes, using NASA data, and the variation of gravity as a function of altitude. It had lots of features that don't apply to bullets, but for fun I decided to model the characteristics of a .44mag fired straight up, plotted at 0.01second intervals. It said the bullet reached about 5000ft altitude, and the whole trajectory took something like 35 seconds (IIRC), and the terminal velocity was almost exactly 300fps.

The impact dynamics calculated above match the terminal velocity of that .44mag round, and what it'd do if it hit someone in the head.

Smaller bullets would probably be more survivable, the MBs 9mm weighs 120gr., half what the .44mag weighs, and it may well have a different Cd. Still, I'd expect it to fall at closer to 240fps than 150fps. But the smaller cross-section also means you have to divide the impact force over a smaller area, so the pressures are still high. Don't forget, it still has to stop in about a 1/4inch, too, so it's decelerating at the same rate as the .44, calculated above.

You can plug in the 9mm's numbers into the same equations and solve for those forces and pressures, and see if they look harmless.

The .44's numbers looked very lethal to me.

My memory may be faulty, but I thought the MBs used the 9mm and a 30.06 rifle for those tests. The question I have about your model is does it presume a stable aerodynamic shape or can it account for roll and yaw disturbances? My aero experience has more to do with cars and it seems to me that you need a pretty slick stable shape to have a Cd of .3 but I know these things don't seem to scale well at small sizes.