Mr Rawles,
I saw the letter you posted asking about the ballistic protection afforded
by common building materials. I did some experimenting on this topic,
testing the protection of concrete-filled blocks against a number
of common calibers. You can see my findings here:
http://www.clairewolfe.com/wolfesblog/00001296.html and here: http://www.clairewolfe.com/wolfesblog/00001404.html
Even 8 inches of concrete offers only temporary protection from rifle
ammunition (though it's quite good against pistol fire.) For info
on other materials, you might direct folks to: http://www.theboxotruth.com/ -
Ian