Ok. Definite correction to my post.
Burt shoots TOWTM through the hand with a 5.56 instead of .50AE. I think my assumption still stands though. If the 5.56 would penetrate (over penetrate the hand?) then I assume the center mass shots would penetrate as well. So, the theory of some sort of body armor or steel/ceramic plates over vitals could well be true.
So, we have TOWTM knowing that he has a vulnerability and protecting himself. He still puts himself in a vulnerable position by going into
the Tower alone. One headshot and he is toast, right? He went into
Dunbar with an army that he let rush ahead of him. So he wasn't as vulnerable there.
Maybe, just maybe, when he got to just CJ left, he didn't have enough Zed shields around him to soak up all the bullets she had. That potential vulnerability may have led him to say "Leave her" instead of taking any chances.....
Probably not fully thought through or put together, but might give some insight into TOWTM.