It has never been 'proven', considering that the Report has the magic bullet entering Kennedys back too low, -- to exit at his adams apple and then strike Connally -- who was sitting even lower.
Not to mention, most diagrams showing Connolly and Kennedy are wrong...in fact Connally was sitting more towards the center of the car than Kennedy...and when you adjust the diagrams to take that into account you find the "magic bullet" did nothing magical at all. It's flight path was pretty straight.
Its flight path was too high, according to the autopsy diagrams in the Report itself, and the zapruder film, which shows Kennedy sitting erect, even leaning back a bit as he waved..
All the 're-creations' try, and fail, to explain away the Reports flaws, and what our lying eyes show us in that film.
Read the definitive work on the JFK assassination:
Case Closed by Gerald Posner