#8 or #9 lead bird shot --- my other light bags are filled with "heavy" sand that you can get from Hart or Sinclair.
I've heard that lead filled bags are illegal in certain competitions.
It was crowded yesterday at the range --- so much that I told a fellow shooter who just arrived at our range --- that I was calling it a day, so he could grab my shooting table. He started to help me pack my stuff off the shooting table...meanwhile thinking he was going to lift my sand-filled rabbit eared bag off the table --- you should have seen the look on his face --- when he tried to lift my lead filled rear bag off the table.
He said..."What have you got in there?" --- after almost dropping the bag off the shooting table.