[Shooter 2.5]

This clip shows only the instant of impact and the initial explosion of JFK’s head.

The moment of impact when Kennedy's head moves 2.3 inches TOWARD THE FRONT. That part is correct. You should have quit while you were ahead.

[ALASKA]

You should have quit before you started. As I said, JFK's head (body) was ALREADY moving toward the front and downward at the time of impact. This was his reaction to the shot that transited his neck. The impact of the bullet to the head instantly and VIOLENTLY drives his head toward the left rear of the limo. The clip you posted is out of context; watch the entire Zapruder film.