Many articles on this over the years on FR.
Here’s a good explanation:
http://www.dailymail.co.uk/sciencetech/article-1338112/U-S-Navys-supergun—electromagnetic-rail-gun-obliterates-targets-100miles-away.html
Damn, I thought the last word of the truncated title would be ‘space’ and Rods of The Gods were now online.