We built a really good range out on the farm. We used the front end loader to scrape into the ground about 2 feet and then brought in more dirt and piled around it. We then used railroad ties to "Secure" The walls by stacking them on top of each other and then nailing them together with a tack strip. It looks like and oversized horseshoe pit. The back wall is about 3.5-4 feet thick and has stopped everything that has bee shot into it for the last 20 years.
High Mountain Hunting Supply