FJs vs Helos? I suspect you don't even need to use a weapon to hurt them! I can remember a F3 going over a Winnebago in RED FLAG at around 720KIAS and around 500-800ft AGL (the ground was about 7,000ft AMSL so the jet was doing about M1.15 around the edge of the overland supersonic area) - the supersonic shock wave dragged the Winnebago off of the road and rolled it over several times. A similar shock wave would wreak havoc with a helo and the blades would take a right pounding - also I remember a supersonic pass on an airborne Herc causing an overstress being registered on the Albert!
LJ