You can not make that deduction in regards to CE 399 going through JFK. The bullet that penetrated JFK in his upper back was not tracked by dissection of the neck organs. That's a fact. The evidence from physical examination of JFK by the prosectors, and witnessed by two FBI agents, pointed to a shallow wound of entrance. The use of a metal probe failed to penetrate beyond the shallow wound despite JFK's lungs being removed. The bullet that struck JFK in his upper back could well have been "defective" and had less powder to propel the bullet at full velocity or it hit something in line with the trajectory to sufficiently slow it down.
JFK was given cardiac massage and it was possible that the bullet had dislodged without anyone noticing it as he never was turned over at Parklands.
Sorry Tony, but you're making this much more complicated than it really is, hence your confusion. Try to stay focused and follow along.
We know the bullet that hit JFK in the back didn't fall out during cardiac massage and go undiscovered in his casket or in sheets at Parkland, here's why;
We can definitively prove the bullet that entered his back had to exit his throat by the process of elimination.
Once again, since there is no exit wound for a bullet that would have entered JFK's throat and no bullet was found in his neck we must conclude that the throat wound was an exit wound.
Let that sink in.
Anterior throat entry is impossible because there is no exit wound for a frontal entry throat shot and no bullet found in the neck.
You're not going to seriously postulate that a bullet entered JFK's throat and fell out during cardiac massage too, are you ?
Sorry, but we absolutely CAN deduce that 399 transited JFK.
SINGLE BULLET FACT