¯ Roy J. was discussing "Armed And Dangerous" with Wayne. ®
 WT> In order to get a projectile moving that fast out of a sling,
 WT> you'd first need to whirl the sling at a speed equaling the
 WT> muzzle velocity of a Civil War rifle.  If you did, you would
 WT> hear a constant sonic boom from the sling breaking the sound
 WT> barrier, and there would be a definite "crack" along the flight
 WT> path of the projectile from the shock wave generated in
 WT> super-sonic flight.
RJT¯Aw,  c'mon,  don't keep us in suspense!  How fast would you have
RJT¯to spin that sucker?     :-)
Well, in order to get the projectile supersonic (just above the
speed of sound), in rough numbers, it would have to be traveling
faster than 1,150 feet-per-second (fps).  Things like
altitude/barometric pressure, humidity, and ambient temperature all
play a part in what the "actual" speed of sound is, but 1,150 is a
fair average, and is used by most shooters.
So, in order to get a projectile moving at twice the speed of sound,
the sling would have to be moving in excess of 2,250 fps.  And
frankly, I don't think anybody can swing a length of leather that
fast...
Now, I'm NOT saying that a sling isn't a weapon that is capable of
causing instant death or injury.  For one thing, a sling is usually
used to accelerate projectiles weighing far more than an average
rifle or pistol bullet.  And since the projectile weighs more, the
speed of delivery can by much less, and still deliver similar energy
to the target.
If you want to play with some numbers, you can use the following
formula to figure out how many foot-pounds projectiles of varying
weights will deliver at various velocities:
 2
V
------- X PW = E(ft-pounds)
450,240
                                                  2
In other words, multiply the velocity by itself (V ) in FPS (for
example 750 times 750) and then divide by the constant 450,240 and
then multiply by the projectile weight (PW) in grains (470 grains to
the ounce). The result will give you the impact force (E) in
foot-pounds.
                              \x/7
.45 ACP:  ONE-HUNDRED years of successful practical testing!
... My Home first aid kit holds thirty rounds and my travel kit holds eight!
---
 * ¯ NRA Life Member, 1972 ® *
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