I don’t think that’s right. Once the apex of flight is achieved it just falls. It can fall fast and pick up speed, but wind resistance will eventually slow it to some max speed (e.g., a human body would be about 200mph IIRC). I doubt it will be anywhere near the same as the original muzzle velocity of over 1000 FPS.....
That said, it’s speed and energy falling could very well be enough to penetrate a human skull on the ground. Still very dangerous.
If shot straight up it will return with dangerous but not necessarily lethal velocity. If shot in a parabolic arc it will return to Earth with lethal velocity.
In tumbled free fall it hits terminal velocity below lethality. If not tumbling, it’ll be fast enough to kill.