I've tested several calibers and versions of bullets at various speeds in water and dirt, and I've only seen good things. The alloy matters more than the hardness. Air-cooled alloy at 18-20 Brinell behaves distinctly differently than heat-treated or water dropped alloy that tests the same hardness. WW with added tin doesn't like to shatter, even at impacts close to 2500 fps. It will lose some weight though, in fragments, but as I calculated, this in moderation ends up a lot like a jacketed bullet.
