Thanks,
@Elderberry . These were tested at the Naval Weapons Lab across the river from where I used to build seawalls.
Many, many moons ago I remember first noticing that we saw the splash of impacting rounds in the Potomac before hearing the report of the guns over there, and realized the shells traveled faster than the sound...
58MW of excess capacity for the Zumwalt class is a lot of juice, and it's perhaps a difficult choice between keeping connections clean and dry vs having powder magazines to detonate in the event of a well aimed hit. IIRC, it was the cost of the projectiles which has been the biggest bugaboo.