The physicist Luis Alvarez demonstrated long ago that shooting an object can make it move in the direction the shot came from. He used melons wrapped in tape to simulate a head. Apparently the ejection of the contents (melon pulp or brain tissue) in the direction of the shot causes the outer portion to recoil towards the shot. At any rate, the muscular response to a severe head injury is far out of proportion to the effect of the bullet. Watch R Lee Ermey shoot some melons on Mail Call. Stuff sprays out of them, but they don't go anywhere.
There was a show on a year or two ago where they built two torsos of ballistic gelatin, complete with human bones, placed them at the proper range and in the proper positions, and fired a shot from a Carcano, using ammo from the same lot of surplus Western that Oswald used. Interestingly, the ammo was apparently manufactured by Western for the CIA for use in the Bay of Pigs invasion.
At any rate, the shot penetrated the upper back/neck of the Kennedy torso, tumbled and struck the back of the Connelly torso going sideways, exited and went through the wrist model, hit the thigh model and bounced off. Other than the lack of penetration into the thigh, it was a perfect match for the Kennedy magic bullet shot. The spent bullet even looked almost identical to the JFK bullet. They found later that their shot had hit ribs on both sides of the Connelly torso instead of only one side in the historical shot, which they thought was why it didn't penetrate slightly into the thigh as the actual shot did.
