Not exactly true. Saw a video a long time ago of the different projectile types they could design.
Once the gun goes from 1.5 to 6 or 7 megajoules, it will be quite literally like being hit by a smallish meteorite. Not the tiny type that puts a half inch hole in your roof...
Envision a hard shell over a slightly softer core like a tank sabot round, about the size of 2 liter bottle of soda... hitting your building at something under 7000 miles an hour (10,000 feet per second). It doesn’t just make a small entry and exit. It does the same thing that shooting a watermelon with a rifle does but on a vastly larger scale. It really IS at least as powerful as hitting the target with a Tomahawk.
So what would actually happen inside your theoretical aircraft carrier just after the first bulkhead or two would look a lot like this: http://www.youtube.com/watch?v=-tTAYFSnRW4
They already stated that it would be very good at destroying whatever is inside of hardened concrete bunkers.
They could even make fragmentary rounds that would explode and damage every aircraft on an airfield enough to keep them from flying.
Amazing stuff.
1. The projectiles lose their velocity and kinetic energy rather quickly thanks to the same atmosphere that attenuates the meteoric junk that hits our planet. The faster it shoots, the more material the projectile loses to air friction heating.
2. Explosive fills, fuzes, electronics for guidance and safe and arm circuitry can't survive the heat, acceleration forces or EMPs generated by these launches - so all they shoot are smallish metal slugs which go "somewhere". Accuracy won't be at all useful beyond relatively short distances.
This is one of those technologies that really wows the bystanders and soaks up the RDT&E funds but doesn't yield very much for militarily useful effects.
That’s gotta sting a little.