You're wrong simply based on where the bullet was found. It was not found in JFK's head.
The working theory is that it passed through JFKs back and throat, made a right hand turn and hit connelly in the back, passing through his wrist and ending up in his thigh. It was almost virtually undamaged. Both of those things made it the 'magic' bullet.
https://en.wikipedia.org/wiki/Single-bullet_theory