Exactly what is a 5.56 or similar going to do to a rotter?
A bit too late for that.
you need to physically 'take them apart'.
A Mossberg(or whatever your fave brand is) pump-action shotgun loaded with 'something heavy'(ie; anything but birdshot) or 40mm grenade launchers is more like it.
Crowbars, machetes, axes, or anything else that can be used to chop off arms and legs is also good.