Great reference!
There was a serious issue last year at one of my local ranges. There was a guy shooting a 9mm pistol at a portable target stand which was positioned about 10-15yds. out. A bullet went through the target, glanced off of the ground, cleared the mound at the 100 yd. distance, traveled almost 900 yds. before penetrating one pane of a dual pane window of a lone house behind the range. Needless to say the owner of the house wasn't too happy when he showed up at the range. At first, no one believed that a 9mm bullet from the range could have traveled that far but after some investigation, they determined that the bullet did, in fact, come from the one person who was shooting a 9mm pistol at the time. He ended up paying for the $3500 custom window but it could have been much worse. The window that was damaged was a children's play room.
The range now has increased the height of the backstops considerably and there are no portable targets allowed, now. Every target has to be placed directly in front of the backstop.
Have you guys ever shot tracers? It's a real eye opener when you can see how often bullets ricochet away from even properly constructed backstops.
Here's some entertaining tracer videos, (some a little less responsible than others!):