You are quite likely a very good engineer and may have done well in physics, but some of us experienced in war time scenarios might disagree with you with regards to how a human body reacts when shot.
Enough said.
There were people present on the grassy knoll who were combat veterans also. They described one or more rounds passing near them, and said they recognized the sensation from their own experience.
So do you doubt them too? Their testimony was contemporary, and on film.