Well for all the rhetoric out regarding Defense Distributed an their successful 3D printing of firearms. It would appear they’re not the only ones looking at printing weapon systems.
The U.S. Navy is apparently considering whether they can re-equip at sea.
It’s an interesting concept. Store enough raw metal. Or even smarter IMHO, engineer a ship where said metal would function as armor or added redundant strength. And allow the ship to convert that into munitions. Yes, canibalize itself if it needs too. Perhaps this makes more sense for a space based naval ship which can grab an asteroid and extract material.