Military, police, and other knowledgeable gunners whose lives depend on proper tactics know that you stay away from hard walls and don't take a prone position on the ground if cover is available. Why? The angle of incidence does NOT equal the angle of reflection. A round will come off of the wall, floor, or other hard object at a lesser angle and hug the wall, floor, or other hard object. This means any round fired into the wall you are close to has a very good chance of success in impacting you. FWIW