I know that hydrostatic shock can be a source of much discussion and debate, so I am not going that direction other than to say that my understanding was that velocity was one of the major factors in that idea. Now, looking at the Hodgdon manual and .300 RUM loads, it shows 180 grain bullets at a max of around 3200 fps, and .300 WM at 3050 fps. I have shot several deer with the Win mag, and never had this problem. I use a Nosler Partition and shoot them in the crease behind the shoulder. My exit wounds are generally around an inch in diameter. I have also shot dozens of deer with a .280 and 140 grain partitions, and doubt that I could have told the difference in the damage. This brings the question of kinetic energy to mind. Obviously, a .280 and a RUM have vast differences in energy. What confounds this for me is looking at a 45-70 shooting a 300 grain bullet at much lower velocity, but creating more kinetic energy than the RUM and again, nothing close to that damage. Now that I have made this as clear as mud, why does the RUM create this kind of damage? I still stand by my idea of poor bullet selection in many cases, but I also agree with BoilerUp on the idea that there was poor shot placement on this particular deer. This is definitely interesting if the damage is unique to this cartridge, but a look at the reloading data does not really suggest that to me since we are talking about an advertised velocity difference of 150 fps.