TG-
This is a photo of the small round hole in the rear of Gov. JBC's assassination-day shirt.

This small round shirt-hole was actually enlarged twice, legitimately, once by the FBI and once by the HSCA, to test cloth for metallic residue. The initial hole was even smaller, but unfortunately it appears there are no photos of the original, even smaller hole.
JBC's surgeon, Dr. Robert Shaw, who worked on 700-odd wartime bullet wounds while serving in the WWII Army, was of the opinion that JBC received a direct shot from above and behind, which left an ovoid wound,
north-south on JBC's back, per his drawing of the wound.
Shaw expanded or debrided JBC's back wound to remove dead flesh and any foreign material, leading to confusion about the actual size of initial wound later.
In addition, the exit hole in JBC's assassination-day suit is also small and round, indicating the slug was
not tumbling as it exited JBC.

I conclude the slug that struck Gov. JBC's back was
not tumbling, in concordance with the sentiments of Dr. Shaw, a very experienced surgeon, with no evident axes to grind.
The "tumbling bullet" appears to be among the many myths subscribed to by LNT'ers, or CT'ers, regarding the JFKA, in order to buttress their narratives.
https://www.tsl.texas.gov/lobbyexhibits/jfk-suit