As a retired Marine I have thought about trying to LEGALLY get access to gunnery ranges to retrieve the shell casings from their gun runs. I imagine the possibilities is less than 1% due to any duds being out there. I would strictly be out there for the brass, I would not touch any other ordinance (in fact could notify them of any possible live ordinance), but probably not going to happen. When I was stationed at Camp Pendleton we had several combat towns out there, and they were usually pretty littered with spent brass, and even then I was able to see the scrapping possibilities.