# Mythbusters... Heres one to think about!



## huntducksordietrying (Sep 21, 2007)

So I was reading stimmies post in archery about a Mythbusters show he saw. I am bored outta my mind so I will post a question that I had about a Mythbusters show I saw a while back. It was the one on if a rifle fires a bullet strait up in the air and it came down and hit you in the head would it be lethal. The test they did figured the terminal velocity of a bullet in a wind tube of a sort. The thing that got me thinking was when I pictured the bullet, how ever high she may go, up in the air, my mind couldnt picture the bullet flipping over and coming down point first. Here is why. In their test they had the bullet point down, in my mind it would come down with the boat tail or flat base first. I was thinking about my .260. Now at 2972 fps and a 1:8 twist the bullet is leaving the muzzle spinning at an incredible rate of 267,480 rpm. (feel free to check my math and correct my if Im wrong) This centrifugul force is going to be slowed by the air Im sure but it wouldnt stop the bullet from spinning. Would not this force keep the bullet facing point up on its way back to earth if the bullet was shot exactly strait up and there were no wind to push it off this vertical coarse? If so then the terminal velocity of the bullet would have been even slower than what they had figured it to be, which I dont remember what it was. Anyway. Something to think about. In the end they determined it would probably not be fatal but it sure would screw your noggin up.


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## Nueces (Jul 22, 2008)

Every now and then unfortunately you'll see in the news after New Year's or something where someone across the country fires in the air and the bullet comes down and hits someone in the head and kills them. I'm sure that is a random angle and not a pure 90* as they may be a mile away.

I agree - I still don't want to be hit in the head by any free falling projectile. I've seen what a little hail pellet can do to a car.


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## mikevanwilder (Nov 11, 2008)

Wow Science class all over again. Anyway wouldn't the heaviest part of the bullet fall first? which would be the base. But still that would hurt pretty bad.


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## apollosmith (Jun 29, 2008)

mikevanwilder said:


> Anyway wouldn't the heaviest part of the bullet fall first?


I doubt it. The aerodynamic force pushing against the back of the bullet would quickly cause it to rotate over to the most aerodynamic angle - tip pointed down. Consider bombs dropped from aircraft or aircraft themselves stalling in the air. As they fall, they quickly point nose down.

Either way, I prefer not to be on the receiving end of any object falling at terminal velocity.


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## truemule (Sep 12, 2007)

I don't think it would fall in any type of controlled or spiral decent. Once it reached its highest point assuming it was a perfect 90 degrees angle and no other forces like wind were pushing it. I think it would start to fall tail first, but eventually would start to tumble uncontrollably. Until it reached a speed where the riflings could actually have an effect on the bullets path it would be too close to the ground to stabalize and gain enough velocity to actually do lethal damage. 

Bombs fall tip first because they are stabalized by fins. Much the the vanes of an arrow stabalize it in flight. These fins are huge and able to grab a llot of air compared to the size of the bomb and its rate of decent. Riflings are very small and loose there effect at slower speeds.

It would hurt like hell to be hit something like this falling but probably wouldn't kill you. I think the news reports are more like Neuces was saying. Someone firing a gun at more of a horizontal angle and whoever/whatever it hits, it hits more in the arc path of the bullet when its still traveling under the velocity of the original shot, rather than its decent after stopping and falling back to earth.


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## cklspencer (Jun 25, 2009)

take a bullet and toss is up in the air and see which end falls first.


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## huntducksordietrying (Sep 21, 2007)

You guys are missing my point. Its the bullet spinning that makes me think its would stay tip up. Take a bicycle wheel. Hold it at the axle and have some one spin it. Now try to flip the wheel over. If you notice the gyroscopic force that resists the changing of the axis. Now I want to know how many of you went out and pulled the front tire off your bike and tried it. Take an arrow for example. Remove the tip and fletchings. Now put the arrow in between the palms of your hands and give it a good spin as your toss it strait into the air. It should fall strait back down with the end that was down coming down again. This is how I picture it in my head. I could be wrong. I agree with you all on not wanting to get hit in the head with a falling bullet. Ouch! :shock:


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## cklspencer (Jun 25, 2009)

I know there is an issue in long range shooting and I know with a muzzy it is easier for this to happen but if a bullet fired in a horizontal plane can TUMBLE then why could it not tumble on its way up. A bullet shot in a horizontal plane tumbles and is still spinning. there is also the point at which the bullet will travel as high as it can go and at that point it would experiance zero G forces or close to zero G forces. at which point the bullet could tumble end over end.


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## DallanC (Jan 13, 2009)

A muzzleloader projectile tumbles easier because it has a low Sectional Density. Bullets with a Higher SD will resist tumbling more and will stablize quicker, penetrate deeper.


-DallanC


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## hyperduc (Sep 18, 2009)

huntducksordietrying said:


> You guys are missing my point. Its the bullet spinning that makes me think its would stay tip up.


A bullet with even a degree of horizontal travel will hit the ground long before stops its rotation, that is assuming the rifling and maximum velocity adhere to the Greenhill formula for stabilized projectiles. Seriously..at any angle/velocity (that satisfies the Greenhill formula) the bullet will always hit the ground before it stops spinning. This of course does not take into account any other influences outside of drag Force is proportional to F = -kV2 though air at sea level, at a specific standard temperature and humidity.

So you are correct it would more than likely still be spinning when it hit the ground tip up, but tip up or tip down the drag difference at terminal velocity would only result in a difference of a few mph.



DallanC said:


> A muzzleloader projectile tumbles easier because it has a low Sectional Density. Bullets with a Higher SD will resist tumbling more and will stablize quicker, penetrate deeper.-DallanC


The drag on a bullet with a low coefficient of drag (as derived from sectional density) and a much lower maximum velocity are the primary reasons that a ML projectile will tumble even after being properly stabilized. Higher sectional densities do not correlate to higher stabilization rates, they do however require lower maximum velocities.



cklspencer said:


> there is also the point at which the bullet will travel as high as it can go and at that point it would experiance zero G forces or close to zero G forces. at which point the bullet could tumble end over end.


At the apex of the trajectory there is a period when there is no motion, gravity however is always present. Both gravity and drag influence the speed of a projectile, but the lack of vertical motion would not influence the rotational speed of the bullet.


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## Nueces (Jul 22, 2008)

huntducksordietrying said:


> Take an arrow for example. Remove the tip and fletchings. Now put the arrow in between the palms of your hands and give it a good spin as your toss it strait into the air. It should fall strait back down with the end that was down coming down again. :shock:


Not quite the exact example you said since the flething and tip were still on an arrow in another case. An arrow was launched close to 90* into the air from a bow. Surprisingly in calm winds, they came down with the tip still in the air and would break over for what ever reason a second or two before impact in the ground and stick in with the weighted field tip.

Certainly not recommended to try. Any clear air disturbance could significantly alter the estimated point of impact! -)O(-

Regarding the random bullets fired in the air that strike people - yes, that is what I was referring to, a shot far from 90*, something more in the 30* range which I believe is the maximum trajectory you can get.


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## hyperduc (Sep 18, 2009)

Nueces said:


> something more in the 30* range which I believe is the maximum trajectory you can get.


an initial vector of 45 degrees will provide the longest horizontal range.


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## Nueces (Jul 22, 2008)

Here's a table showing a .308 with impact speeds and total down range:


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## Kevin D (Sep 15, 2007)

Don't know about the spin or anything like that, but one time as a kid I fired my .45 Colt straight up into the air for kicks and giggles. I was in a swampy area and when the bullet finally landed about 30 yards away it hit with enough force that it would've cracked your skull open if it would have hit you. It was one of those stupid things I'd never try again.


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## Nueces (Jul 22, 2008)

Ya - check out the 8th column with bullet impact speeds in the image above.


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## BPturkeys (Sep 13, 2007)

I don't understand row 10 (90 degree angle)...straight up... "Speed at Maximum Altitude"...seems like that should be "0". Wouldn't the bullet keep going up until it stopped...speed "0" and then start back down??


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## hyperduc (Sep 18, 2009)

The application that produced those tables appears to have some rather obvious flaws, I can see at least three examples where common physics have been defied.


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## DallanC (Jan 13, 2009)

hyperduc said:


> an initial vector of 45 degrees will provide the longest horizontal range.


That is true... in a vacuum.

-DallanC


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## hyperduc (Sep 18, 2009)

DallanC said:


> hyperduc said:
> 
> 
> > an initial vector of 45 degrees will provide the longest horizontal range.
> ...


That's true in ANY medium, including air. Even the flawed ballistics chart got that part correct.


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## Packbasket (Oct 29, 2009)

well, I guess the old geezer will kick in here and we'll start with the old rule that education can be had at any age but wisdom only comes from experience.

never cared for that one myself til I was old enough to see its truth.

First, bombs do NOT land point down unless purposely engineered and stabilized to do so, they continue along on the path they were released at, they don't fall like bugs bunny cartoons but rather hit the earth at an angle, bombs that do not detonate can be backwards mathed and you can tell how high and how fast a plane was travelling when it released, this is fin stabilized bombs as others touched on, bombs that are designed to tumble like napalm are canisters and generally cartwheel along once the liquids get the balance thrown off.

Second, 45 degrees is NOT the 'highest angle of trajectory' unless in a vacuum, on earth it varies by location and gun.

In exterior ballistics this is called "Maximum Horizontal Distance of Gun" and if we have any FAC, Pathfinders, battleship guncrews or artillery men on here they will tell you that the calculations for MHDG varies by gun, but as a general rule for small arms fire MHDG is around 30 degrees.

A bullet will fall base first unless acted upon by wind or other forces ENOUGH to overcome gravity, the heaviest section will fall first, as stated above.
climb on the roof and drop a whole mushroom, try to even get one to land stem down first, this is why buttered toast always lands buttered side down when you drop it off the table, the buttered side is heavier. 

Anyone whoever watched the Mercury, Gemini, and Apollo missions can tell you that the capsules didn't come in point down, they came in base down, had to, sheer physics dictated they would as soon as ANY gravity played on them.

ever have your mushroom anchor or duck anchors land mushroom end up in the mud and only the rope end be down? ' course not. can't happen unless an outside force acts on it to make it so and overcomes gravity.

all bullets fall at the same rate close to earth as any other object, 32.15 ft/s, minus friction.
The bullet will not be falling at the speed it ascended being fired, as only gravity will be acting on it, minus friction as it falls, we are saying no wind but there is still air, correct? Still gravity and rotation of the earth? if not then the bullet won't fall at all, so don't worry about it.

I very much doubt that a bullet will travel far enough away from earth to effect a change on gravitional field, but if it does you will have to recall your calculus as this will involve a non constant acceleration of g, gravity of earth, but even small arms will undoubtedly fall no where near you if fired perfectly perpendicular to the earth since where you were on firing is no longer there, the earth has moved but the bullet has not, it's still where you were when you fired it.

A man can not step into the same stream twice, as both the stream and the man have moved.


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## hyperduc (Sep 18, 2009)

Packbasket said:


> Second, 45 degrees is NOT the 'highest angle of trajectory' unless in a vacuum, on earth it varies by location and gun.


I don't think anyone made that argument, what was said is that maximum horizontal distance is achieved (in any projectile not subject to lift) is achieved at 45 degrees. The type of gun and location have no bearing upon laws of physics. The formula above, the provided ballistics table and every single physics book on the planet support this theory.

The reason that gunny and crew use a max of 30 degrees elevation (I really have no clue if this is true or not) has nothing to do with that being the degree of elevation that yields the maximum horizontal distance.

FWIW I'm not trying to call anyone out here, I'm just trying to make sure someone gets the right answer. If I am wrong I would love to know.


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## Artoxx (Nov 12, 2008)

This is a funny argument, and is sounds like several different physical assumptions are being used to calculate the various answers that are being given.
All I know is I saw several different experiments involving how fast various objects fall from various heights. The only thing I am sure of is that IN A VACUUM an object falls at a specific rate of speed. I think it is 25 feet per second per second. maybe 28? IDK.
Anyway, the experiment involved whether or not a penny dropped off the Empire State bldg would or would not kill a pedestrian if it hit them in the head.
The answer regarding a penny was a resounding NO. Not a great experience, but not fatal.

Taking drag from atmosphere into account, it was even less likely to be TRULY dangerous.
SO. Are any of these theories presented here actually right? IDK. 
One thing that I do know is that bread does NOT fall butter side down due to the weight of the butter as Packbasket stated. That was actually disproven by my 11th grade applied physics teacher, not to mention MYTHBUSTERS. lol 
We used the step ladder method.

_*They*_ tested buttered and unbuttered bread dropped from heights from 2.5 feet or so (average kitchen counter height or thereabouts) up to about 20 feet high, (off the roof of a building) and many heights in between including twice the height of the first measurement (2.5 feet-5 feet)
The result was that THE ROTATIONAL SPEED determined by the bread dropping off the average persons hand was just enough to flip the bread over halfway before it hit the floor, thus putting the butter side down. When they put the same person on a step ladder so that their hand was exactly twice as high up, the bread landed BUTTER side up, having made a full rotation.

From the top of the building, the bread actually averaged the butter side landing UP more often than not.

Not that this is truly relevant to the bullet danger theory but I thought it was amusing.

It has also been proven that the vast majority of random injuries and deaths resulting from bullets fired at random into the air, were the result of LATERAL movement not vertical. At least that is what the articles I have read on the subject said.

That is my $2.50 on the subject, 2 cents just donesn't cover it for me. :mrgreen:


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