Bullets fired in the air

Cecil's Columns/Staff Reports
21

[QUOTE=minty green]
In the case of the Mythbusters episode, they went out to a dray lakebed and set up a rig to point the gun straight up. (I think it may have been angled slightly to account for wind speed and direction.) Then they emptied the clip and waited to hear the rounds hitting the ground and searched the desert for the holes.

They found several impact sites from the handgun they tested (9 mm, I think), and measured the depth at which the spent round was located inside the hole. From that measurement, they calculated the force required to embed the round at that depth (which was consistent for all the located rounds). The results were in the same ballpark as General Hatcher (described above) had found.

They also tried the experiment with a rifle, but were unable to locate any impact sites after the rounds returned to earth, apparently because the rifle launched the rounds high enough that the winds carried them too far away to locate. So to simulate a straight up, straight down fall by the rifle rounds, they rigged up a balloon to drop them from sufficent altitude to reach terminal velocity, then again measured the depths of the recovered rounds.
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Couldn’t they use tracers?

22

Yes, I know this is a zombie thread…

[QUOTE=minty green]
If by “experiment,” you mean literally firing bullets straight up into the sky, finding where they landed, and calculating the force necessary to embed the rounds in the depth of the earth where they were collected (which was consistently ~3 in., IIRC), then yes, I guess you could say that all they did was an “experiment.”
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Well, yeah, that is an “experiment.” Your phrasing makes it sound like you think it’s not an “experiment”?

[QUOTE=minty green]
It was a hell of a good experiment, and the results convincingly demonstrated that a bullet falling back to earth after being fired straight up will not strike with sufficient force to kill anyone. If you have any specific criticism of the methodology that casts doubt on their results, I would be interested to hear it. Barring such criticism, the results appear pretty conclusive.
[/quote]
The Mythbusters guys are pretty good at designing experiments to demonstrate something. What they’re not so good at is figuring out whatever the something is that they’re supposed to be demonstrating. The results of their experiment (at least, from the description of it in this thread; not having seen the episode, there might be some nuances of which I’m unaware) showed that if you fire a non-rifled bullet of a particular caliber directly straight up in the air, then most of the time, it won’t kill you when it lands. That’s a far cry from the more authoritative statement you made. Specific criticism follows the next quoted part…

[QUOTE=minty green]
As the Mythbusters episode noted, however, bullets fired in a more general “upward” direction can remain in a ballistic trajectory and return to earth with force sufficient to kill. It seems likely that this is the explanation for the cases noted in Cecil’s column.
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Sure, I’ll buy that. So how far away from “straight up” does the bullet have to be fired in order to “remain in a ballistic trajectory”? I don’t really know. However, I don’t think anyone would interpret the “myth” that’s being “busted” here as relating only to bullets fired exactly vertically. Is an 80 degree angle sufficient to keep the bullet in the required trajectory? Seventy degrees? Sixty?

And, as noted above, it’s possible the spin of a rifled bullet would stabilize it, preventing it from tumbling and increasing the terminal velocity. Not tested.

How about different size bullets? Different aspect ratios? Does that make a difference? I dunno.

And, what Dex was getting at: It’s a jump to say that if one or two or ten bullets hit the ground at a certain speed, then they all will. Suppose 99% of bullets fired into the air tumble on the way back down, but the remaining 1% stabilize themselves and therefore drop faster. What is the minimum number of tests to say with confidence that this is not the case? Particularly combined with my first criticism?

23

t-bonham, you probably should have started a new thread and just linked to this one

24

Bumped.

A young fatality from this in Florida, alas:

25

Ugh.

I unfortunately work evenings in an area where celebratory gunfire is common. We’ve picked up multiple spent bullets off the tarmac the day after New Year’s/4th of July and one year a solar panel was damaged bad enough to need replacing. However the worst was several years ago when a graveyard shift worker was standing just outside a door on a concrete pad on New Year’s and a spent bullet missed him by a couple of feet. It made a nice divot in the concrete that’s still there. Did it hit hard enough to kill? Probably not. Hard enough to crack a skull/cause a nasty head wound? Probably.

26

As I recall, I thought that “Mythbusters” or maybe some other show found that a bullet fired straight up into the air would come down flat, as opposed to tumbling or point first. But that might have been specific just to the rounds they were firing. Still would be pretty painful.

27

Just a few notes on this zombie thread. First and foremost - anyone interested in this topic should obtain a copy of Hatcher’s Notebook written by Julian Hatcher of the US Army. The entire book is a fascinating read about many aspects of damage caused by firearm misuse. Hatcher was an expert witness back in the day.

Hatcher’s method was straightforward when you have the Army at your disposal. They mounted a 30 caliber machine gun on an adjustable stand pointed vertically. They set this up on a wooden pier that went a long way into a small lake. They would fire a burst of rounds and wait. A minute later the bullets would begin splashing down and since they fired multiple rounds it gave them a chance to observe the impact zone, which they could not do when only single rounds were fired. The gun was adjusted and they shot again. They eventually got bullets that dropped in a small area right around the (covered) firing point. They were able to catch bullets in buckets or have them impact the pier.

All the bullets landed base down. None tumbled since they were still spinning at 200,000 rpm or whatever. They even unloaded bullets and re-inserted them backwards so they fired base up to see if the point-down bullets would fall faster. They did not.

RE the before mentioned parachutist who released bullets while he fell - since the bullets were not rotating at high rpm it has little bearing on this topic.

Hatcher tested other things that are urban legend like. What happens when you fire a bullet by itself (no gun)? What happens when you shoot a canister of gunpowder? Can a match that ignites in a shirt pocket set off a cartridge? (Actual court case).

One of my favorite descriptions was of the “shoot the canister of gunpowder” experiment. A sharpshooter sat down about 60 feet away from the canisters. They started with a 1 pound can and then shot progressively larger canisters. 5 lb, 10 lb, etc. Nothing happened as they expected. But things changed when they got to a larger canister. In retrospect the taller canister had enough height of gunpowder that the lower section had compressed enough to detonate. The bullet struck near the bottom and the resulting explosion bowled the shooter over backwards.

The Mythbusters staff contacted me early in their career to discuss falling objects. I was the facility manager of NASA’s Zero Gravity Facility at the time. That conversation was in regards to the “penny drop” myth and would have been possible to test in the 5 second free fall drop that was obtained in the facility. Having never heard of the Mythbusters at that time I was doubtful we could have accommodated them. Alas, the idea fell through much to my later regret.