I store it in a Stack On
GCB-900 cabinet that I have added silicone strips around all openings to make it a sealed environment, in which inside is a
rechargeable silica gel passive dehumidifier. The intent is for the humidity level to be lower than in my high security safes. For common use rounds, I just use those plastic storage containers you can find just about everywhere, and a few of the
Plano organizers that I use for fishing tackle that I sometimes use the dividers to separate different lots. However,
the single most useful product for me is this...it is fast, easy, and allows me to easily label just about anything. I can stick it on top of a specific compartment and then label it as I want.
I have placed a secondary lock on these cabinets for a little more security, and I have 4 of them bolted together to increase the size and mass in the event someone wants to steal it. I also use these cabinets for other items that I want to keep out of the reach of wandering eyes, but not valuable enough to put in one of my security safes (ex: powertools, Shimano reels, bench rest accessories, pricier office supplies, older laptops, older smart phones, etc.)
For very long term storage, I will put the rounds inside an empty factory box, label it with those Post It Note tapes, and then place that inside a Ziplock bag. When I do this I first leave the cardboard box exposed inside the locking cabinet for a few weeks so that the silica gel removes any moisture that may have built up in the cardboard...otherwise I would have concerns that if the cardboard is even slightly damp that by placing it in a Ziplock bag I would trap more inside humidity than I want for that type of storage (even though it is probably not that big of a deal.)