I ahve a bullet in my hand right now. I can bounce it off of my arm and the desk and it does not show any major damage. It all depends on the bullet's velocity at the time it is moving. Also, where do you get this "90 degree turn" stuff? Connaly was turned around when the bullet hit him and it's trajectory shows a straight line back through him, through Kennedy's wounds, and on to the 6th floor of the book depository.
Here is what Governor Connally said on the subject:
They talk about the "one-bullet" or "two-bullet theory, but as far as I'm concerned, there is no theory. There is my absolute knowledge, and Nellie's too, that one bullet caused the President's first wound, and an entirely separate shot struck me. No one will ever convince me otherwise. It's a certainty. I'll never change my mind (DiEugenio 101).