I've seen a few references to them (turret factories), and possibly a screenshot, but I can't for the life of me find out whether they're currently construct-able, and if so, how to do so. It doesn't seem to be listed within any of the station founding tabs insofar as I've tested, but I also could've missed it somehow (not large enough founding ship, needs to be attached to an asteroid).
I'm not too concerned, as it's not an immediate requirement, but once I progress a bit further, being able to arm my other ships without playing the lottery against enemies or trying to find sufficient shops will be quite convenient.