When I was a teenager, I tried making up some salt loaded shells by removing the lead shot and replacing it with rock salt. The results were very disappointing because the salt didn't have enough weight to cause complete burning of the powder charge.
I the early 1970's I was on the staff of a school that taught bomb disposal to civilian police, and during that time we obtained some commercially loaded 12 ga. "Riot" shells. They contained plastic pellets about the size of BB shot, and worked very well for shooting open packages. As I recall, the instructions were to use ricocheting fire at close ranges, and direct fire only at 50 yards or so.