There was a range near me that had a documented problem with bullets leaving the range. They eventually installed barriers just above the trajectory of "on-target" bullets so that it is nearly impossible to shoot above the target backers, much less the berm, when seated at the bench.
There's a private range on county land here. They added eyebrows, and added additional barriers underneath, on the ground, so rounds couldn't skip off the range floor. They also added barriers at the top of the berm so that rounds couldn't skip up the berm and go off the range.
Nowadays the only rounds that hit the nearby industrial park come from he adjacent Sheriff's range.