The most common warhead for the Hydra 70 rocket is the M151 "10-Pounder," which has a blast radius of 10 meters and lethal fragmentation radius of around 50 meters [REF].
NOTE: Though some of the warheads described were designed for the older Mk 40 rocket motor, but most likely could work with the Mk 66 motor if upgraded or modernized models were not available.