[Shooter 2.5]

I've been in commercial buildings such as that. You could see the lower floor from the cracks in the flooring.

You are correct as far as how thick the planking is, though.

What I left out was they described the dust falling on their heads with each shot.

[Ronin]

Weird. We are talking about a book depository, aren't we? Books are heavy. Very heavy. I can't imagine how much weight is already on that floor, but it is obviously strong enough to hold up all the books.

Despite that, they describe dust falling with each shot and hearing the brass hit the floor.

Seems weird to me.