sentences:  Together the two guns would give the ship a rate of fire of 24 rounds/minute, giving them the throw weight of two 6-gun 155 mm artillery batteries.Precision munitions make gunfire three times more effective than unguided shells, hence the DD-21 was said to have the destructive power of six batteries.The Navy's goal was to have 256 VLS cells on the DD-21, but the final number may have been 128 - some sketches show missiles being launched from fore and aft but the aft launchers appear to have been replaced by a second gun system and/or a helicopter pad.