The rifle was a 6.5mm military rifle. All of the 6.5 mm military rifles at that time were loaded with bullets of full metal jacket, either spitzer or round nose design that weighed between 140 and 160 grains. (whether Swedish, or Japanese, or Italian) the Italian version carried a 162 grain round nose. Bullets of that high sectional density would have NO problem penetrating a human head, or body, and still penetrating a windshield. Not saying where the hole in the windshield came from, I’m just saying it could come from either direction. It may not have been “incoming’
The more I watch that film, the more it looks like the shot trajectory was upward and out of his skull.. Obviously not a forensic expert, but I don’t see any way any gunman either in the book depository or on the grassy knoll could have produced that angle.... Sure looks to me like the fatal shot anyway was from inside the vehicle.
Pretty sure I read somewhere a SS accidentally discharged their gun when reacting to the shots fired... and if true that would explain many things.