The US Navy gets all the best toys....

http://www.popularmechanics.com/technology/military_law/4231461.html

 

Eight megajoules sounds like a lot. Sometime, I'll have to work out what it took to accelerate a 2700 pound 16" AP round to something like 2600 fps. Converting to MKS will take a minute or two.

That seems to come to 96 megajoules for the 16" shell.