Just to clarify the capabilities of those mass drivers, and note, this is back-envelope work.
So, we’re going to stick a big dumb projectile in the breech. By big, dumb projectile we mean a 2400 mm k-slug of soft iron (iron being cheap as dirt, and really, what it’s made of doesn’t matter all that much in this application), and we’ll call it a 2400 mm diameter cylinder, 4800 mm long. That’s 22 m3 of iron, massing 173 metric tons.
If we crank a Leviathan primary up to full power, we’re going to be sticking about 10.1 exawatts (usable) in the flash accumulators; that’ll accelerate that projectile at around 1.1 million gravities for close to a second, meaning it leaves the muzzle with a velocity of 0.036 c, i.e., in the low-relativistic regime. Impact energy delivered to the target is on the order of 2.4 gigatons.
This, needless to say, is way too much boom for almost all practical applications, and no-one routinely stocks that kind of k-slug or runs their mass drivers at that power level, not least because it’s gonna take enough time for the shipboard powerplant to put ten exawatt-seconds in the flash accumulators that you sure aren’t going to be able to fire one of those shots every second, or anything close enough to it to avoid being a big, fat, wallowing target. There are uses for Mighty Glaciers and uses for Glass Cannons, but there’s no use at all for something that’s both.
But if you happened to be interested in what the hardware could deliver if you wanted to comically overkill something with no means whatsoever of fighting back, there are your numbers.