“They were built for the rail gun.”
And how many of those do we have, exactly?
L
http://www.huffingtonpost.co.uk/entry/watch-the-us-navy-test-an-experimental-railgun-that-can-fire-projectiles-at-mach-6_uk_58d3a100e4b0b22b0d1a0901
They’re on back order. :)