If you're anything like me you are using a full size cabinet to store your ammunition. It works well other than the fact it's supposed to hold firearms/shotguns so doesn't have any shelves (obviously)
Cleared out:

Some 12mm Birch faced ply, and a bit of door stop later:

I'll probably add some more shelves as this is by no means all the stuff that came out!

And here's both cabinets:

Pictures are from my boing & it's a bit dark so not the best!