The simplest, safest (to the shooter) and most twisted round is called the "cut-shell".
Using light bird shot, you merely cut the circumference of the plastic just over the wadding with a deep groove. When you fire the shell the entire shot charge comes out as a projectile encased in the plastic casing. When it strikes a target its something like a hand grenade going off.
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Keith
The Bears and Bear Maulings Page:
members.xoom.com/keithrogan