According to Steve at hammer and their website, the Hammer Hunter with the drilled hollow point expands into 4 petals and shear off both forward and radially and fragging. The remaining half looks like a wad cutter pistol bullet pushing through, or to, the off side.
Check out their website or call Steve. He can clarify further. It just doesn't turn into microscopic pieces like many cup/core bullets are known to do. They have a customer in Africa who reported back with 13 kills and all the terminal details if you're interested, Shep. Good read.