Really cool gif, it's got me on a trail of slow motion videos.

The way the bullet flattens made me remember an anecdote I heard in an archery class. The instructor did a lot of work in film and television and his biggest job was as some kind of archery consultant/co-ordinator for the movie Braveheart. There is a scene where hundreds of arrows are fired and the director wanted this shot from the ground as the arrows were falling on top of the camera. The plan was to get the cameraman sitting in a little bunker with bullet-proof glass for protection. The archery instructor explained this was not a good idea by shooting an arrow through a sheet of bullet-proof glass (although looking back he may have been exaggerating this aspect, he probably just explained the principles behind why it wouldn't work).

The reason the glass broke for the arrow and not the bullet was that the bullet-proof glass is designed to deal with the bullet breaking apart and spreading out on impact, whereas the arrow maintains its form, and the point would break right through the glass.

I've believed this story since I was quite young but if it's bullshit and that's not how bullet-proof glass works then someone needs to tell me.