I use empty tea or water bottles. Fill them with water and they make great demonstrations. We did it last week. Shot one jug with a 9mm, it made two nice little entry and exit holes and the water drained out the holes. Shot the next jug with a .45. It made bigger holes and the water drained a bit faster.
Then we shot the last one with a .44 mag! It blew the jug into pieces spraying water and jug parts about 6 feet into the air and backwards about 6 feet!
That makes quite an impression.
And we still got to eat the watermelon.
