#1. They are not made commercially, and never were. They have to be hand loaded.
#2. Shooting someone with one today is a FELONY crime in most places.
As far as the law is concerned, fire a gun at someone, and legally it doesn't matter if it's a load of buckshot, a load of rock salt, or a load of feathers.
You just SHOT someone.
Better have your legal self-defense ducks lined up real good, and be ready to explain yourself in a court.
#3. These days, shoot some intruder with rock salt, and he will likely blow your head off with HIS gun, which won't be loaded with rock salt.
#4. Even if the above doesn't happen, care to guess what the shoot-ee and his relatives will do to you in a court room during the multi-million dollar law suit?
#5. Rock salt will rust a shotgun barrel in very short order.
#6 Rock salt collects moisture from the air and sticks together in large clumps.
Shoot at someone to dust him, and WOW, will you be surprised when the solid clump kills him.
Bottom line.
The "good ol' days" when you could pepper some punk kid or intruder with rock salt are LONG gone.
Shoot someone today, NO MATTER WHO THEY ARE, OR WHAT THEY WERE DOING, and YOU'LL be the one in BIG trouble, both criminal and civic.
To be as clear as possible:
These days, shoot someone with rock salt, no matter WHAT they're doing, and you'll be spending the night in jail.
Then the REAL trouble will start for you when the prosecutor and lawyers come after you.
Don't believe it, ask any cop, prosecutor, or lawyer.