IMO a hog is not great b/c you have no control over many variables and the results may not be apparrent. Did the bullet hit a bone, even glancing? What angle was the entry? etc., etc,. I would prefer a test that is consistent. Ballistic gel alone is not a great medium for sure. I have been thinking about this for several months and trying to come up with a way to simulate clothing, skin, sternum, and then flesh (ballistic gel) consistently.
The major problem is the sternum. What is cheap and has characteristics nearly identical to the sternum?
Of course, I am not trying too hard as my wife has a masters in forensics and I haven't even asked her yet.
The real problem is people translating ballistic gel results directly to results on targets.