The big, multi-drawer steel ones are the way to go, as long as you have the floor space!

A mate of mine who is a SERIOUS cartridge collector has a couple of them for his collection. In the bottom of each drawer is a sheet of corrugated cardboard, "groovy" side up. This has been sprayed with the stuff artists use for "sealing" charcoal sketches and the like. This prevents any residual acid from the manufacture of the cardboard making the brass cases go "green", and acts to stiffen the cardboard under the weight of the ammo.

The only problem is that these cabinets are heavy; then again, you will have great difficulty over-filling one and the better ones have ball-bearings in the telescoping steel runners. Most are BIG, (A0 size) so you need a bit of floor space. You could use the vast expanse of the top of the unit to show off your artillery stuff, (or shooting trophies), I suppose. The basic drawers cabinets are also stackable. (If you put legs under them, watch the point-loading on the floor when you fill them full of brass and lead!)

I have also seen these steel drawer units used for storage of "collectable" handguns, amongst other things. Most places that used these drawer systems for maps, architectural drawings, etc., have changed over to "vertical" plan-hanger units. The big advantage of these is that you are not forever shuffling and unloading (thus damaging) the documents.

Some of the "flat" cabinets have lock systems or, being steel, can easily be fitted with external lock bars etc.

Seek out your local purveyor of "used" office fittings and furniture.