I posted this on "When Was JBC Hit?".
It demonstrates what nonsense the premise of this thread is.
The observation, that JBC doesn't look injured at z248, is utter nonsense;
"I created this GiF to highlight JBC's reaction. I used z223 and z240 which represents a time gap of 1 second. A single second. Look at the difference between the two images and consider there is a single second between them:"

I agree that there has been only one shot by z240. z240 is quite consistent with JBC doing what he said he did, and what Nellie and Gayle Newman and Bobby Hargis observed JBC did, in response to the first shot. In fact, Hargis thought that JBC was hit on the first shot because of the way he reacted.
The problem with your scenario is your insistence that JBC falsely imagined he was not struck on the first shot.
It is also at least interesting that JBC does not move his right arm after z271. In z240 he has yet to swing his right forearm from somewhere below to right in front of what would become the chest exit wound.