Really? I find that fascinating because I’ve had about the same experience and for about the same number of years and with melons and so forth.
But you’d have to put a melon on some kind of spring or something to behave as the neck. But aside from that, with the ballistics experts that show bullet tracts through that jell-o stuff on TV, the bullet does more damage if it tumbles, hasn’t gone through something solid or partially solid first and so on, but even those don’t simulate a head moving attached to a neck and body, they are just big blocks of Jell-O sitting on some kind of table or something.
In reality, if Oswald shot him 3 times, the third (kill)shot would have gone through the back of his head and splatter would have gone all over Conally, not Jackie. and I’m reasonably certain that his head/body would have snapped forward.
Physics is a science, and the observations you've scene that are different from mine just prove my point.
Kennedy's head reaction to the third shot was exactly what I would expect from a shot from behind blowing out a chunk of his skull just above his eye socket.