Hi Mr. Rawles,
I read your reply reharding “EcoBeam Construction for Ballistic Protection”.
Three years ago, a friend of mine and I shot a concrete wall until we made a nice size hole in it [1]. This was just to see how much small arms fire it could take. [We used handguns.] Here is a web page I made about it with photos.
Readers will get a idea what you meant about sand and and gravel being better at stopping small arms fire than even reinforced concrete.
Take care, – Wes