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Tito_Muerte
2004-Nov-15, 03:06 AM
No, this isn't a Steve McQueen question...but in all fairness, he should get a forum of his own.

Anyway, my roommate asked me the other day, as we were watching those zany palestinians shooting into the air, about why people aren't killed by those bullets when they come down. The best answer I could give him, was that bullets reach their highest point, and then start to fall like any normal object, so that they really wouldn't be any more dangerous than medium sized pieces of hail. Any of you physics grads have anything to add to that? (And I do mean just the physics people, or someone with a definitive scientific answer. I don't need a reply restating what I just said).

frenat
2004-Nov-15, 03:17 AM
Some people are killed by those bullets. I have heard of it happening but many of the bullets fired just don't hit anybody.

Humphrey
2004-Nov-15, 03:21 AM
People were injured and killed by the bullets fired into the air During Arafats funaeral.

frogesque
2004-Nov-15, 03:30 AM
From Snack Talk (http://www.exo.net/snaktalk/hypermail/0091.html)

The book Sport Science, by Peter Brancazio, contains these approximate
terminal velocities:
raindrop = 15 mi/hr
baseball = 95 mi/hr
golf ball = 90 mi/hr
ping pong ball = 20 mi/hr
On a web search I found a value of about 300 ft/sec (that's roughly 200
miles/hour) given as the terminal velocity of a .30 caliber bullet. I don't
know for sure that this is valid, but it seems reasonable, especially in light
of the values for the baseball and golf ball noted above.

200mph terminal velocity for a lump of lead can do a lot of damage to a skull.

Joel Clifton
2004-Nov-15, 03:34 AM
Bullets, especially pistol bullets which are bigger and stouter than most rifle bullets, will fall fast enough to injure or kill someone they hit. An AR-15 bullet (.223), which is only about 55 grains, will probably not do serious damage, but a .308, which are about three times heavier, would be pretty bad. AK-47 bullets are the same caliber but a little stouter than .308 bullets, and are just as heavy, so they could do serious damage.

But the liklihood of a bullet hitting someone is rather slim because their high speed gives them a huge possible target area, so that's why it doesn't happen much.

I know a bit about the size, shape and weight of different calibers because I'm kind of a moderate gun nut. Among other guns, I have an AK-47 and AR-15.

Evan
2004-Nov-15, 07:04 AM
know a bit about the size, shape and weight of different calibers because I'm kind of a moderate gun nut. Among other guns, I have an AK-47 and AR-15.

Falling rounds can and will kill people. I was trained by the US military. Even a .223 round can kill when it falls from the sky.

Charlie in Dayton
2004-Nov-15, 10:05 AM
"Just remember -- a speeding bullet is nothing more than a lump of lead with the proper incentive." -- someone else

swansont
2004-Nov-15, 12:02 PM
Anyway, my roommate asked me the other day, as we were watching those zany palestinians shooting into the air, about why people aren't killed by those bullets when they come down.

The only reason more people aren't hurt is that the cross-section of a person is usually small compared to the total area the bullet could hit.

Stuart
2004-Nov-15, 02:39 PM
why people aren't killed by those bullets when they come down.

The simple answer is that they are, routinely. When Saddam Hussein was captured, the inhabitants of Baghdad celebrated by firing barrages of gunfire into the sky. Eight dead, eighty wounded. There have been a lot of similar cases including incompetently-discharged firearms killing people at considerable distances from the point of discharge. A good few years back, close to where I lived, a woman was on the roof of her house, adjusting a TV antenna when she suddenly collapsed and fell off. Her husband thought she had slipped and fallen, ran to her and saw she had been shot through the head. The bullet (7.62 x 51mm) was eventually identified as having come from a rifle range seven miles away

iFire
2004-Nov-15, 02:45 PM
why people aren't killed by those bullets when they come down.

The simple answer is that they are, routinely. When Saddam Hussein was captured, the inhabitants of Baghdad celebrated by firing barrages of gunfire into the sky. Eight dead, eighty wounded. There have been a lot of similar cases including incompetently-discharged firearms killing people at considerable distances from the point of discharge. A good few years back, close to where I lived, a woman was on the roof of her house, adjusting a TV antenna when she suddenly collapsed and fell off. Her husband thought she had slipped and fallen, ran to her and saw she had been shot through the head. The bullet (7.62 x 51mm) was eventually identified as having come from a rifle range seven miles away

Not to sound insensitive or mobid, but, thats one hell of a shot. :o

Stuart
2004-Nov-15, 05:50 PM
Not to sound insensitive or mobid, but, thats one hell of a shot.

More like horrendous, hellish bad luck on the part of the victim. Apparently an negligently discharged shot just cleared the safety berm behind the targets and her head was in the way of the ballistic arc. The bullet had completely lost stability by then; it was literally one in millions of it hitting her head and penetrating her skull.

Which exhibits a great truth about handling guns; its necessary to know what's beyond the target because Murphy's law says if it can hit something that will cause trouble, it will.

Evan
2004-Nov-15, 06:24 PM
Stuart,

The maximum range of the 7.62 NATO ball round when fired from an M14 is 3725 meters. That is six miles.

ngc3314
2004-Nov-15, 06:42 PM
Stuart,

The maximum range of the 7.62 NATO ball round when fired from an M14 is 3725 meters. That is six miles.

I call bad units conversion! 3725 meters is more like 2.3 miles...

Stuart
2004-Nov-15, 06:52 PM
Stuart,

The maximum range of the 7.62 NATO ball round when fired from an M14 is 3725 meters. That is six miles.

I think you'll find that is the longest effective range; this shot was way beyond "effective" range. We can check the range easily enough though; the bullet was fired at Bisley rifle range and the woman was killed in Lightwater. I'll do a check, see what that distance is.

***EDIT*** Did a check - I found this map

http://www.yourmapsonline.org.uk/MapSurrey.JPG

The area is in the top left hand corner. The distance looks to me to be around three miles rather than six - -t may be I misremembered kilometers as "miles". It was a really foul bit of bad luck. I'll look some more see if I can find reference to the story - it was way before internet days though.

iFire
2004-Nov-15, 07:01 PM
If the person was lower in elevation, regardless if she was within or outside the bullet's effective range it might be in its "luck range".

Evan
2004-Nov-15, 07:24 PM
Yeah, I knew it looked wrong. It is 2.31 miles. That is listed as the maximum range of the M14, not the maximum effective range which is 460 meters. That really isn't the case though. I could hit a half man target 8 out of 10 times with iron sights at 400 yards with the M14.

Stuart
2004-Nov-15, 08:02 PM
Yeah, I knew it looked wrong. It is 2.31 miles. That is listed as the maximum range of the M14, not the maximum effective range which is 460 meters. That really isn't the case though. I could hit a half man target 8 out of 10 times with iron sights at 400 yards with the M14.

That's the effective range of the rifle though, not the bullet. In Afghanistan, snipers are picking off haji at 1200 meters plus with 7.62 x 51. In this case the bullet was way beyond its effective range, it was probably yawing all over the place and tumbling. Incidently, the rifle here would have been a bolt-action Lee Enfield rechambered for the 7.62 x 51. Anyway, have a look at the map I referenced (Lightwater is close to Bagshot)

bobjohnston
2004-Nov-15, 08:24 PM
In my old hometown of Brownsville, Texas, people routinely fire guns into the air on New Year's Eve. My mother-in-law was missed by a bullet that came through the roof and ceiling and was then slowed enough to bounce off a table. In the area there have been people injured and at least one killed from this in the past decade. The pop. density is lower than Baghdad or Ramallah, but blindly shooting guns into the air is still stupid.

Evan
2004-Nov-15, 08:27 PM
Stuart,

How did it happen that someone was firing such a weapon? I am under the impression that all but shotguns are restricted weapons in the UK. It certainly wouldn't be a current military rifle. I also can't figure out why someone would rechamber a Lee Enfield to 7.62. .303 ammunition is widely available, at least it is here and there are still tons of ammo left over from WWII that is available cheap.

frogesque
2004-Nov-15, 08:47 PM
Bisley firing range (http://www.yorkshire-ra.org.uk/html/bisley.htm)

Zachary
2004-Nov-15, 08:57 PM
Surely a bullet would come down at the same velocity that it was fired at, or am I missing something here? :-?

Stuart
2004-Nov-15, 09:11 PM
Stuart,How did it happen that someone was firing such a weapon? I am under the impression that all but shotguns are restricted weapons in the UK.

They are now; this incident took place in the mid-1970s. At that time, rifle ownership was much more common. My father had an SMLE chambered for .303 x 56R back then.

It certainly wouldn't be a current military rifle. I also can't figure out why someone would rechamber a Lee Enfield to 7.62. .303 ammunition is widely available, at least it is here and there are still tons of ammo left over from WWII that is available cheap.

The SMLE was (and as far as I know remains) the standard interclub competition rifle in the UK. Originally, they were chambered for the old .303 round but when the British Army shifted over from .303 x 56R to 7.62 x 51, it was decided that the standard for competitions would be changed as well. People were given the choice of having their rifles rechambered for the new round or giving them up and using rifles supplied by the range. The argument for the change was that the range was British Army property and they didn't want to keep two types of rifle ammunition on range. Also, because it was an interclub competition venue, the weapons used by the various clubs had to be standardized (otherwise some smarty like me would turn up with a scoped Dragunov SVD and have a major - and quite unfair - advantage). So the rules of the interclub shoots were - SMLE, iron sights. The clubs had to use Amry supplied ammunition as well, again in the interests of a level playing field.

That's assuming the shooter was a civilian - remember that Bisley was a British Army range and the Army snipers back then still used scoped Lee Enfields chambered for 7.62 x 51

swansont
2004-Nov-15, 09:18 PM
Surely a bullet would come down at the same velocity that it was fired at, or am I missing something here? :-?

Drag from the atmosphere. Air resistance will slow it down.

Joel Clifton
2004-Nov-15, 09:42 PM
Surely a bullet would come down at the same velocity that it was fired at, or am I missing something here? :-?

As Swansont said, it's due to atmospheric drag.

When, for example, a .223 bullet exits the gun, it is traveling around 3000 fps. Within about 300-400 feet (.1 to .15 seconds), the bullet will have slowed to about 2700fps, which is about the slowest the bullet can travel and still fragment (the fragmentation is what makes them so effective).

Zachary
2004-Nov-15, 09:45 PM
Surely a bullet would come down at the same velocity that it was fired at, or am I missing something here? :-?

As Swansont said, it's due to atmospheric drag.

When, for example, a .223 bullet exits the gun, it is traveling around 3000 fps. Within about 300-400 feet (.1 to .15 seconds), the bullet will have slowed to about 2700fps, which is about the slowest the bullet can travel and still fragment (the fragmentation is what makes them so effective).

Bah, stupid mech lessons ignoring real life factors 8-[

Bob B.
2004-Nov-15, 09:51 PM
I calculate a terminal velocity of 153 m/s for a bullet traveling point first through air at sea level density.

For those who feel like checking up on me, here are my figures:

Assume:
7.62mm bullet weighing 10 grams (154 grains).
Drag coefficient (Cd) = 0.15 (typical for a bullet traveling less than 0.5 Mach)

Given:
Air density at sea level (rho) = 1.225 kg/m^3
Acceleration of gravity (g) = 9.80665 m/s^2

F_gravity = m*g

F_drag = Cd*rho*V^2*A/2

m = 10 g / 1000 = 0.01 kg
A = Pi* (7.62/1000/2)^2 = 0.0000456 m^2

Terminal velocity occurs when F_drag = F_gravity

m*g = Cd*rho*V^2*A/2

0.01*9.80665 = 0.15*1.225*V^2*0.0000456/2

V = SQRT[0.01*9.80665*2/(0.15*1.225*0.0000456)]

V = 153 m/s (502 ft/s)

Of course, the actual velocity would probably be less because the bullet would likely be tumbling or traveling sideways.

Evan
2004-Nov-15, 09:58 PM
Surely a bullet would come down at the same velocity that it was fired at, or am I missing something here? :-?

Drag.

frogesque
2004-Nov-15, 10:07 PM
Thanks for the computation Bob B

153m/s = 342mph, a bit higher than the estimate of 200mph given by the link I quoted earlier. Whatever, it's still enough to give you a VERY bad headache and spoil your day if one hit on the way down.

Bob B.
2004-Nov-16, 01:26 PM
153m/s = 342mph, a bit higher than the estimate of 200mph given by the link I quoted earlier.
Don't forget that my calculations are for the optimum condition, i.e. with the bullet falling point first. Any other orientation would result in a lower terminal velocity. Let's say it is falling base first and we have a drag coefficient of 0.5 (a guess) instead of 0.15. Now we have a terminal velocity of 84 m/s, or 188 mph.

Finding the right drag coefficient is always one of the hardest parts of these types of computations.