Like me you have probably been following events in Libya. Something that has been seen commonly on the news reports has been that of jubilant rebels firing large numbers of bullets up into the sky. Although one can understand this expression of excitement, have you ever wondered what happens to these bullets. Well what goes up must come down.
Because of the American domination of all things to do with firearms all measurements to do with ballistics are in old units. No SI here. Velocities are in feet per second, calibres are in inches and weights, of bullets and powder, are measured believe it or not in grains, rather like drugs in the UK until the advent of metric units. 1 Grain is 64.8mg.
A high velocity bullet, such as that fired from an AK47 leaves the muzzle at 2300fps. For comparison a low velocity round such as a .38 pistol has a muzzle velocity of 900fps, still highly lethal.
A falling bullet attains a terminal velocity of 300fps, while 150fps is sufficient to penetrate the skull, so a falling bullet is not something you would want to hit you on the head. Apparently gunshot wounds have a surprisingly low mortality of only 5%, but falling bullets are far more likely to hit you on the head and have a staggering mortality of 32%.
In 1991 the end of the first gulf war was celebrated in much the same way as we are now seeing in Libya, and falling bullets killed 20 people.
What a pathetically stupid way to die.
If they go _straight_ up, they fall back at terminal velocity (about 150 mph for a bullet). At this speed, they are no more dangerous (nor safe!) than an airgun round. They cannot kill. [There's a Mythbusters episode in which this is tested to destruction.
ReplyDeleteFatalities/ severe injuries occur when random shots are fired at less than 75 degrees - the bullet can then take a ballistic path and still be carrying some of its muzzle velocity (which is all lost in the straight up/ fall down scenario).
So nice story, but only C- for the Physics.
In Mythbusters bullets were simply dropped from a height. They had no stability, were able to tumble and thus had a much lower velocity. A fired roud will still be spinning enough to make it stable enough not to tumble, and will thus have a considerably higher terminal velocity than an unspinning projectile.
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