A mate of mine being a chippie has made a weapons & kit cupboard out of MDF & has done it a way that it blends in with all the furniture
He's done it in an alcove and has disguised the front as a normal display cupboard so you can't see any evidence of the alcove
As I don't have the room in my bedroom, I've got 2 cupboards with a work bench between them, all the small items go under the lowest drawer in both cupboards & rifles, bags & other large items are under my bed so I have it on wheels to roll out