OK found it. It is in the Speer Manual #12, page 109. I was wrong on the names. It is
motus violentus. The area immediately in front of the muzzel. The bullet is not fully stabilized FULLY after the violent transition from the chamber to bore to free flight.

motus mixtus portion of the bullet path where normal stability occurs induced by the effect of gunbarrel and rifling.

motus naturalis, portion where velocity is dropping and is shedding velocity and stability, again becoming varible.

The arch described by the bullet path is parabolic arc, which is more complex than a simple cicular arc. Check more out on a google search of "Short, medium and long range ballistics"