If you're a diver and come onto land and shoot at AI it acts as if it barely hurts them. I would think it would do more damage than what I have seen. I found this out myself playing around in map editor and just noticed it in a video on youtube where others have the problem. Hoping its just a bug that needs tweaked as I can't believe that ammo would penetrate that horribly on land especially if its a head shot.
Here is the video showing the problem, go up to about 11:15 and start watching.