[TheForge] OT - Yak Gun question

[James Binnion]

It sounds like it can.

from http://www.straightdope.com/classics/a950414b.html


> At first I thought being struck by a bullet falling straight down  
> would be no worse than getting hit over the head with a two-by- 
> four--not the average guy's idea of fun, but not fatal either. What  
> goes up must come down, but it needn't do so at the same speed. You  
> run up against what's known as "terminal velocity." A bullet fired  
> straight up will slow down, stop, then fall to earth again,  
> accelerating until it reaches a point where its weight equals the  
> resistance of the air. That's its terminal velocity.
>
> For further insight, we turn to Hatcher's Notebook (1962) by Major  
> General Julian S. Hatcher, a U.S. Army ordnance expert. Hatcher  
> described military tests with, among other things, a .30 caliber  
> bullet weighing .021 pounds. Using a special rig, the testers shot  
> the bullet straight into the air. It came down bottom (not point)  
> first at what was later computed to be about 300 feet per second.  
> "With the [.021 pound] bullet, this corresponds to an energy of 30  
> foot pounds," Hatcher wrote. "Previously, the army had decided that  
> on the average an energy of 60 foot pounds is required to produce a  
> disabling wound. Thus, service bullets returning from extreme  
> heights cannot be considered lethal by this standard."

snip

> "Still, the question isn't how many people get injured or killed by  
> falling bullets, it's whether such things are possible at all. On  
> further investigation, it appears the 60 foot-pound injury  
> threshold cited by Hatcher may be misleading--a falling bullet's  
> kinetic energy (foot pounds) alone is not a good predictor of the  
> speed it needs to inflict a wound. B. N. Mattoo (Journal of  
> Forensic Sciences, 1984) has proposed an equation relating mass and  
> bullet diameter that seems to do a better job. Experiments on  
> cadavers and such have shown, for example, that a .38 caliber  
> revolver bullet will perforate the skin and lodge in the underlying  
> tissue at 191 feet per second and that triple-ought buckshot will  
> do so at 213 feet per second.
>
> Mattoo's equation predicts that Hatcher's .30 caliber bullet, which  
> has a small diameter in relation to its weight, will perforate the  
> skin at only 124 feet per second. It's easy to believe that such a  
> bullet falling at 300 feet per second could kill you, especially if  
> it struck you in the head."
>

James Binnion
jbin at well.com