You also need to look at the standard the court will be applying ... most likely "any possibility whatsoever that....."Let's assume at the outset that these bullets did not, in fact, come from the range. You can try to establish that in court. Difficult and not cheap. Whether or not a higher berm helps is less relevant than whether the court could be convinced that it did. FWIW, it sounds like skipping off the ground is the only way a bullet leaves this range. A higher berm might help a little bit, but maybe there is a specific mitigation for that possibility. Maybe a low wall of some kind. I don't know.