Absent a recovered bullet, no credible ME is going to speculate what caliber, bullet style or or even type of firearm was used. This is solely about their unwillingness to speculate. They know the difference between big holes and little ones.
They will describe the hole(s) in the hide, the hole(s) through internal organs and membranes and the general direction of travel inside the body. These holes are typical described as 'defects' with a diameter expressed in imperial or metric. The primary and secondary conditions related to the cause death (hemorrhaging etc) will be described.
The reports, photos and physical evidence go back to the agency with jurisdiction for interpretation and usually, follow-ups. That interpretation, by people with decades of experience, is correct more often than not.
If they can't get the interpretation right 100% of the time, small wonder the internet makes such a mess of it,
That makes sense.
