I'm looking to build an Indoor Shooting Range, I live in South Ga, so anything underground on my place will require a steady pump to keep water out so I've ruled that out, next suggestion was to use shipping containers, I have a 40 ton crane and equipment to set and build it anyway I need, however I have never shot a magnum rifle through a container to determine the actual "noise pollution" obviously I would pad the first 20' container and air condition it for the comfort. Im going to put an oehler system in whatever I do. I have a range 800yds on another piece of property but trying to keep things quiet for my elderly neighbors that's closest to my shop. What's your experiences.