Mus, the job title is in Gargoyle's profile.
What type of credentials do mercenaries have? Mercenary credentials, of course!
I too find the query a little odd. I guess I would have figured that somebody in the business would have some insider information on such things. Maybe not. I certainly would have expected that a person in the field would know that bullets are routinely pulled from the dead during autopsy as part of criminal investigations, on a daily basis.
As for where to get reliable data from these doctors, those working on living or dead individuals, there isn't a database. First of all, that concept that 'reliable' is pushing it. You will need a set of criteria on which to determine if the data are reliable. That could range from the basics such as caliber, brand, weight retained, or go to extremes such as noting the consistency of reporting. The work of each doc would have to be evaluated to see if they even know what they are talking about if they do such assessments. Many don't. They pull the slugs from the bodies, bag the slugs, and let the detectives do their jobs. So there may be no doctor data per se.
Unless you find a doc who is doing research specific to the problem, you won't find docs who keep tallies on the slugs pulled from bodies, much less all the specific information needed by someone in ballistics research. No doubt the information is out there in the millions of police case files in cities all over the world, but only as individual pieces of evidence in a larger packet of evidence.
Unit 900 noted .40s penetrating well and doing massive damage. No doubt most rounds have the potential to do this. With that said, Unit 900s statement has an unknown level of reliability to it. This is no slight against Unit 900, only the description give. Without specifics, can any of just judge what "penetrated deeply" means or what "massive damage" means? These are vague descriptors, colorful and give some idea of the extensiveness of the wounds, but still vague. Why vauge? None of us know the context of the things he has seen. Penetrating deeply on a 400 lb man is different than on a 150 lb man. The penetration may be 10" in both cases, but on the 400 lb man, that might only be just getting through the stomach fat whereas on the 150 lb man, it may have gone all the through the chest and finally come to rest in the spine. Massive damage? What is the gradient for light, medium, heavy, and massive damage? Where does one descriptor stop and another start? When we say "massive damage" are we referring to the whole body in general or to just specific locations. I have seen "massive" damage to an eye produced by a BB gun, but the wound itself was fairly minor except for the eye (which was lost).