To believe that both the back and the neck wounds on JFK were entrance wounds requires:
** the shooters to have used low velocity, low power weapons
Even through the z312 shot fragmented, as a result of hitting bone, the skull, at near muzzle velocity, the fragments had no problem going all the way through the skull. One fragment cracked the windshield, another dented the windshield frame while a third flew on another 80 yards and nicked Mr. Tague. It was able to do this because of the high speed (2150 f/s). A similar round would surely go all the way through JFK?s neck, leaving both an entrance and exit wound. JFK?s neck simply would not stop such a bullet, leaving only an entrance wound.
So, to believe that both wounds are entrance wounds, I would have to accept:
** The shooters elected to use a frontal shooter, even though this will tend to make it apparent there were multiple shooters.
** The shooters elected to use lower velocity weapons, even though these are inherently less accurate, particularly with a moving target.
** The shooters elected to use lower velocity weapons, even though these are inherently less lethal than a regular rifle.
** The shooters elected to use lower velocity weapons, even through they would inherently tend to make it appear Oswald was not the shooter, since they would not leave an exit wound.
** And, most fantastically of all, by sheer luck, a frontal shooter and a rear shooter, hit on opposite sides of the neck, allowing the wounds to be explained by a shot from the rear. What a fantastic lucky break for the conspirators.