I wanted a medium that made HP's fail. I never liked Black Talon 45 ACP. They opened picture perfect in water filled milk jugs, but lots of HP's did. Put a couple layers of denim in front and things got iffy quick. I liked phone books because I get them free at certain times of the year and they are definitely tough on HP's. The same as dry wall is.
So for now I'll use my phone books. My testing needs satisfy only me
Mike