And what happened when CE399 Struck/Broke the Radius BONE?
Another easy one. CE399 was travelling at a much lower rate-of-speed as compared to the head shot bullet velocity... thus retaining its front-end structural integrity.
Governor Connally's Wrist Wound
http://mcadams.posc.mu.edu/zimmerman/frontmenu_000024.htm "Governor Connally was seated in front and to the left of President Kennedy. His exact position is not known, as photographs are not pinpoint accurate with regards to his position, compounded with the fact that nobody knows exactly when he was hit. Nevertheless, he was in a position such that a bullet exiting his chest at a downward, right to left trajectory could hit his right wrist. Governor Connally sat in the presidential limousine with his hands across his lap, save for one detail. He was holding onto his gray Stetson cowboy hat with his right hand. Whether his right wrist was lying on his leg or whether it was across his left arm is not known for sure. It is also not know if his arm was resting or in the air. Regardless, he received an entrance wound to the dorsal, or towards the rear (backside), of his forearm, about 2 inches from the wrist on the thumb side.
This bullet shattered the smaller bone of the forearm- the radius.