Have said this before, but no harm saying it again.
As others have said, re-purpose a normal gun safe by adding some shelves. This way you can organise your ammo by calibre & even purpose, eg 308 for stalking on one shelf & 308 for target on another.
You can use a take down shotgun safe or a normal shotgun/rifle safe. I upgraded my ammo storage to this method when I upgraded my cabinet. Your FEO can’t complain about security as he’s already approved the cabinet for rifles so ammo should be fine!
The shelves just need a small amount of DIY skill.
Get some 3mm thick plywood & an old cereal box. Use the cereal box to make a template that you can take measurements off & then cut the plywood into strips that are as wide as the depth you want for the shelves. Then decide how many shelves you want & how big the gap needs to be between them. For each shelf you need to cut two lengths to use as uprights, so same length as the gap you decide you need between shelves, & one piece to use as the shelf itself.
Put an upright in on each side at the bottom, push them out to the side of the cabinet & put a shelf in on top of them - if you’ve measured & cut accurately enough the shelf can be made a slight push fit (side to side not depth) to hold it in place. Alternatively a couple of spots of wood glue on the tops of each upright will be sufficient to hold the shelf in place - once it’s got ammo on it gravity will do the rest.
Then put another upright in each side & a shelf on top, glue if you want, then repeat as required.
One bit of advice, make the gap between the bottom of the cabinet & the first shelf higher than the gap between the other shelves & do the same with the top shelf.
Don’t forget also that the doors have a hidden hinge on them so will need space to close - make sure you allow enough clearance when deciding the depth of the shelf.
