My solution isn't fancy, but it might suit you. I gutted a linen closet and made it into a gun rack.
I cut notches into wood, screwed it into the walls around three sides at the height I wanted for barrel support. Removed outside handles then replaced the original handles with much longer screws through the handles, through the doors and into wooden blocks with 1 1/4" holes cut through. 1" dowel slides through these from the adjoining closet to make a simple but discrete "lock" that is easily opened if you know where to look.
Additionally, you have to know the closet is even there to see it. Must walk into the room and close the door to see the closet, as it is covered by the door when open.