The Beehive round is an interesting round as it is marginally more effective than a 40mm buckshot round.
http://www.ballisticsbytheinch.com/22.html
As for lethality there is a report out of the Balkans conflicts of a Croat point-man who used a suppressed American 180 SMG. The guy would encounter Serbs and let off a burst of 20 or so rounds usually killing the enemy point element before they could raise an alarm.
With a beehive round the bullets would be deflected by just about anything. leading to 18 random trajectories. it might not hit anything but it might make someone duck.