I don't have room for ammo either. In the general scheme of things, the iron is the much larger issue. So I keep ammo in a couple of footlockers in the garage with the obvious exception of the loaded HD weapons and their associated loaded mags.
I'm currently working on a solution for this:
What a delightful yard ornament. I need four of those, one mounted on each corner of the wall surrounding my compound, and controlled by an automated infrared sighting / tracking / firing system.