A lot of the videos I see on youtube for ballistics testing use a wet phone book. However, I haven't been able to find the reason for soaking the phone book. I'm trying to figure out if the purpose is to make the paper softer, so that the rounds will penetrate further. Or perhaps it is the opposite. Maybe the water is there to add density so the rounds will penetrate less. I could see it going either way.
I'm wanting to do some ballistics testing myself, comparing some different types of ammo. I've looked into making gel, or using phone books, or both. Just don't know if I should soak the phone books or not. I'd probably just try it both ways but I don't have many phone books. I have opted out of receiving them the last few years and so I don't have many left.