My home range backstop, back to front....
8x8 wall of sandbags, then,
8x8 wall of 4x4 timber, then,
8x8 frame consisting of 3/4" plywood, 10" of sand, 3/4" plywood, then, 4" of sand, then, 8x8 wall of 4x4.
About every 2 years I have to replace the front 4x4 wall, but have only had a few rounds...