5 feet is more than enough but put wood up in front of it to hang targets from and make sure there is nothing for at least a mile behind you just in case one goes over the berm... it happens at Tulsa gun club and the berm is 20 feet high.
Bullets have been found on the National Guard tarmac
They indeed have. Not any recently that I know of, but the guy that runs our shooting team has found a few bullets. Fortunately before a multi million dollar engine sucked it up.