[lefteye]

A #4 bird shot pellet weighs about 3.24 grains. A #1 buck shot pellet weighs about 40 grains. A #4 lead bird shot pellet will not penetrate nearly as far as a #1 lead buck shot pellet, and, of course, neither will penetrate nearly as far as any lead or solid copper slug. To "stop" the bad guy immediately shotgun pellets must penetrate about 12". A #4 bird shot hit would certainly produce a horrible center of mass wound, but it is much less likely to stop the bad guy immediately.