The solution is to post a sign that says No Trespassing DANGER Private Shooting Range not responsible for property damage of trespassers vehicles. Shoot holes in the trespassers radiators and it is amazing how a long walk and paying for an expensive tow can get the message across.
I still smile about the fools that called the sheriff to report being shot at and then tried to explain why they were hunting on posted private land, designated as a shooting range, that was owned by a sheriff deputy. Funny how they had no clue that cutting a chain on a locked gate just added to the crime.