I shoot with my pond dam as a backstop. Loose about 5% even when I KNOW they are right there in front of me. A couple of years ago I built a 9x10' frame from PVC pipe and put a netting over it. Still lost about the same percentage. I did figure out that the cost of the materials I bought, if I recovered ALL the brass, would pay for itself in about 3950 boxes of reloads.
Since I live there I just go out in the morning and evening and look from my mule (Kawasaki type). The different angle of the sun often lets you see the ones that were actually in plain sight when you shot them.