What type of bullet leaves a square hole?
But seriously, I found this close-up photo and the author theorizes that the straight sides may have been cut for a sample but the other sides appear to be ragged and extend way past 3/8 of an inch.

After a little research into this, the resulting hole in fabric does not appear to be a direct reflection of calibre.



So in conclusion it seems to me that the ragged edges on Connally's shirt hole(measured from each extremity to be roughly 3/4 of an inch) are the result of a tumbling bullet which did not strike flush but at an angle which is totally consistent with Dr. Gregory's estimation of a linear wound with a length of 3/4 of an inch.
Mr. SPECTER - What did the wound of entry look like, Doctor?
Dr. GREGORY - It appeared to me that the wound of entry was sort of a linear wound, perhaps three-quarters of an inch in length with a rounded central portion. Whereas, the wound of exit was rather larger than this, perhaps an inch and a half across.
JohnM
"...it seems to me that the ragged edges on Connally's shirt hole(measured from each extremity to be roughly 3/4 of an inch)..."As usual, I'm having problems understanding what you're posting.
Either I'm missing something very obvious or you are, once again, talking utter nonsense.
So, according to the picture you posted you believe the hole "measured from each extremity" is
ROUGHLY 3/4 OF AN INCH3/4 of an inch?
The hole ACROSS THE DIAGONAL is less than 1/2 an inch.
That means each side is even less than that.

What am I missing?