The little I did know about flash bang grenades is what I've seen in video games and movies
This is exactly your problem. Get the proper informations first, and then come back with some ''real life'' arguments that'll make this thread worth the time of others.
I can start a shitload of threads about "things I saw in movies and games" too, but fortunately i've been on this forum long enough to know better. You'll find out soon too, the hard way or easy way