This one's for Butch.
When I was a kid, one of the leaders of my scout troop, Butch (who passed away about a year and a half ago), had a few stories about this. Butch was a gun collecter, Life member of the NRA, taught Rifle and Shootgun merit badge, and had a collection of firearms at the Cowboy Hall of Fame (just to name a few things).
Anyway, when he was in the Army Core of Engineers (Demolitions, 1950's) in Hawaii, he would often have to pull guard duty. For this, he carried an 870 loaded with table salt (not rock salt). Reason: while rock salt will travel a respectable distance, and sting like crazy, the table salt will burn like hell at close range, and there is nothing to dig out. You just have to sit there and let it disolve (which will take a while).
One story he told involves someone hopping over a fence to get on base. Butch caught him trying to get back over the fence, and put two rounds into his back side (one for each cheek). Who ever it was, didn't sit down for about a month.
After he got out of the army he still kept some table salt rounds arround for home defence. I believe, he had a mossburg bulpup shotgun converted to a left hand eject (he was a south paw, as well as being a machinest), and that was the only gun that was ever stored loaded in his house, with table salt.