I've seen mention of rail guns for military use, but to date the only place they've existed is within the realms of the video game "half-life".I believe the Americans are looking at putting a railgun in a future tank design in around 2015 all going well
If you do a search within Wikipedia, there's a paragraph or two on them there.
Following reading the article, it becomes apparent that rail guns consume huge amounts of electrical energy in the process of creating their "projectile".
From this fact, it can logically be deduced that the most obvious position of use for them is either as a static defense weapon, located close to an easily consumable power supply, or at sea on a ship with the ability to divert all electrical power for the use of the gun (almost instantly indicating that it would be fed from a nuclear reactor/power supply).
From the lack of detail regarding their development across the web, I think it's reasonably safe to say that while the technology is feasable, putting it into development for practical use is probably 10 - 15 years away at the earliest.
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