We just have large ~6' tall x 20' wide mounds of soil at each target interval [7, 25, 50, 100 & 150 yards]. The shooting range is facing a hillside. Little chance of overshooting dangers. As needed, we sift the soil to recover the lead and rebuild the soil mounds.
Initial construction took some time and effort but the range is pushing 40 years old now with only minor repairs needed.