Here is a video of the principals behind the Hydro bullet. It is a Woodleigh promotional video so whether you believe it or not is up to the viewer. It discusses the cavitation bubble. Anyway here it is.

https://www.youtube.com/watch?v=ZN9y6YvTUYk

AS far as deflection in game goes it has been proven years ago that a Meplat on the front of the bullet reduces deflection significantly, one of the reasons many big game bullets are designed in such a way.

Matt.