Quoted:
There's a difference between firing straight up into the air and sending a bullet on a 40* ballistic arc-straight up, it runs out of go and then accellerates to terminal velocity (around 120mph). Ballistic arc allows the round to continue in a spin stabilized flight path as well as carrying a good bit of velocity. Get hit with a FALLING round, and you'll probably just end up with a knot. Get hit with a bullet travelling in a ballistic arc and you're gonna need an ambulance at best, a hearse at worst.
Terminal velocity varies depending on the mass of the object falling, the drag area of the object and the fluid it falls through. A human in a spread-eagle position has a terminal velocity around 120 mph. A human in a streamlined position has much more than that. If you're falling through the upper atmosphere, you can break the sound barrier in freefall. There were bunkerbuster bombs in WW2 that had terminal velocities in excess of 2,400 mph.
But yeah, if the bullet's not spin stabilized, it won't fall very fast.