Camp Shelby is decidedly not one of the high points of the United States. Last time there was in 1992, and backwoods (read backwards) was the best description.

Take good rain gear, and watch out for all the camp followers. Those girls are dying to get out of that area at all cost.

PS: Generally each post in the US has a website that will have a "what to bring" section. Also there will be contact information for Range Control. If you can find someone who will give you a little time, they may have the best info you can get (especially a retired soldier/civilian employee).