A few days ago I saw this video passing by in my suggestions but I was like "meh, gonna watch it later". Now it's as good time as any. And I'm glad I did because it's pretty cool to see how much force an 8 inch glass ball can stop. Even the 50 cal didn't make it all the way through, that's impressive.
So the best bulletproof shield would be a bunch of glass balls, I guess. Unless the sun is out, then you'll burn alive, lol.
Fun to watch. They remind me of Myth Busters like experimentation. The glass and sun reaction was unexpected. They also used good gun safety protocols. Fun!!