There are morons shooting sniper rifles in the game area near us. Land is mostly flat, few rises here and there. Wonder how far those bullets go...
If shooting fairly low, the bullet ought to hit the ground closer. If it is still in flight for one second while holding higher, it may be 2500-3000 ft away when it first hits the ground.
If it then bounces off, it can travel further, repeating, until it runs out of velocity.
Obviously no backstop will work if accidental discharge at a elevated angle or simply having the sights set too high to begin with
Mostly shoot as if your Son, daughter or best friend is standing somewhere downrange, and take steps to prevent your rounds from reaching them by having adequate barriers in between.