“Just what is the terminal velocity of a fusiform boat tailed bullet?...” [going hot, Post 46]
Thanks to going hot for jogging my memory about major factors I left out of my summary in Post 50: air density and speed of sound. They are closely related.
There is no single value of terminal velocity for a projectile falling to earth through the air: many characteristics - of the projectile, and of the air it is falling through - cause effects that vary, sometimes abruptly.
Air density is one of the most important characteristics affecting friction from he air, and thus terminal velocity. Atmospheric density varies, decreasing with altitude - and also with weather conditions such as temperature, barometric pressure, relative humidity, etc. The denser the air, the more friction will slow whatever is going through the air (the aeronautic term for air friction is drag).
Changes in drag due to air density is why Joe Kittinger (now Col, USAF (ret)) reached a maximum speed of 614 mph (about Mach 0.9 at his altitude) when he leapt from a balloon gondola in August 1960, free-falling from over 102,000 ft. Civilian parachustists free-fall from much lower altitudes and in the denser air don’t exceed 120 mph too often.
The speed of sound in air is not a constant but varies according to several factors, the foremost of which is temperature.
This fact affects the trajectory of any bullet that leaves the muzzle above Mach 1.0; above the “sound barrier” any solid object trails a shock wave. When it slows below the speed of sound, the shock wave dissipates. The intensity and angle of incidence of the shock wave vary greatly, depending on the parameters of the atmosphere at that exact location, at that moment - and the velocity of the projectiles. And the position of the waves coming off the projectile can vary so quickly human perception cannot follow them.
Aerodynamic scientists took many years to figure all this out, leading some researchers to predict that human flight above Mach 1.0 would never be possible. They were wrong, but lives were lost during the effort, while difficult research went forward, and imaginative designs were devised to work out the science and produce systems capable of doing the job.
For our purposes, this means that a bullet transitioning from supersonic to subsonic velocity can change direction radically and unpredictably.
All of which means that no one can predict where happy fire might return to earth - not with any certainty.
That would be akin to holding up that book and have the g friend or wife touch off a round!