
Not necessarily. If the body had been denatured (cooked) or dehydrated due
to the heat, a projectile needs only a minimal kinetic force to penetrate.
In fire aftermaths, bodies tend to fall apart or loose large chunks of
meat with little effort. Medical Examiners tend not to like cleaning up
such scenes. 

As such, if the body had been suitably cooked, a bullet comming from a
magazine explosion would more than likely have enough force to enter and
thus it would be difficult to determine whether a bullet entered at the
time of death, or much later, unless you were trained to look for the
evidence. Texas Rangers are not pathologists. 

