Always heard rock salt worked, but never knew anyone who actually used it.
Rock salt DOES work, according to one of my uncles.
As kids, Dad and my uncles were raiding the orchard of an old boy on the island. The old boy heard them and came out of the house raging, with a SxS shotgun in hand. All the older boys saw this and ran like h3ll, hurdling the fence and disappearing in the dark. My youngest uncle was a little slow, as he climbed down out of the tree he was in, rather than jump out, so he just dove through the fence, as he was too small to hurdle it, and climbing would have taken too long.
As he went through the fence, the old guy let fly with one barrel, peppering my uncle's upper thighs and backside, but missing all the important bits. For 3 or 4 days, my uncle was extremely sore, with large welts, and found it hard to sit down. He also had to steer clear of the old fellow, who was travelling the island looking for a kid having trouble walking and sitting. No salt penetrated, luckily, but it stung enough that he never went on another raid of that orchard.
On a side note, I was told by a guy years ago, that if rock salt does break the skin and penetrate, it stings like h3ll for a long time, until it dissolves and is absorbed by the body. What he used was black peppercorns. They are small enough that you can get a pretty good payload in a shell, and are round enough that you get a reasonable pattern. BUT, if they penetrate the skin, they just sit in there and burn like fury until they are removed.
