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Japan Becomes 1st Country Ever To Fire Electromagnetic Railgun From An Offshore Vessel
(www.eurasiantimes.com)
This is a most excellent place for technology news and articles.
From what I see, it looks like they never actually put the thing on a boat. All the testing was on land.
And after years of R&D the US Navy put the project on ice recently. Apparently they don’t think it’s worth the cost.