http://breakingdefense.com/2016/10/general-dynamics-griffin-dont-call-it-a-tank-its-totally-a-tank/

I was reading the above and the new light weight cannon piqued my interest and was curious if it could be scaled up or modified for naval purposes? would a ETC cannon barrel be doable on a destroyer?

They’re certainly viable and can be used for naval purpose.

Regarding ETC tho.. it’s very complicated, and may not warrant any advantage over increasing gun caliber for both naval or army purpose. Better go for full fledged EM Railgun if very high velocity is desired.