Buying in bulk only pays if the ammo still goes bang in year five. Good news: modern ammunition is remarkably durable, and storing it well requires exactly three things — cool, dry, and sealed. Here's the practical version of each.
The two real enemies
Moisture
Humidity is the killer. Moisture corrodes cases, works into primers over time, and degrades powder. The fix is cheap and total: sealed containers with desiccant. Military-style ammo cans with intact rubber gaskets are the gold standard — it's why surplus ammo stored in them for decades still runs. Toss a desiccant pack in each can, recharge or replace it yearly, done. Ammo that ships in a sealed can, like PMC 5.56 in a heavy-duty ammo can, arrives with its storage solution included.
Temperature swings
Heat itself degrades powder slowly — stable warm is far better than cycling. The real damage comes from repeated hot-cold cycling, which drives condensation inside packaging and accelerates everything moisture does. This is why attics, garages, and car trunks are the three worst places in your life to keep ammunition. A closet inside your climate-controlled living space beats all of them by a mile.
The setup that works
- Location: interior closet or cabinet, off the concrete floor (concrete wicks moisture — a shelf or pallet fixes it).
- Containers: gasketed ammo cans, one desiccant pack each. Original factory packaging goes inside the can — it stacks better and preserves lot numbers.
- Labeling: caliber, load, and purchase date on every can. Future-you will thank present-you at 6 a.m. before a range trip.
- Rotation: shoot oldest first, restock behind it. A simple first-in-first-out habit means nothing in your stash is ever more than a few years old anyway.
What actually ruins ammo
Water immersion, long-term high humidity without sealing, oil and solvent contamination (keep cleaning chemicals away from stored ammo — penetrating oils can kill primers), and years of trunk-style temperature cycling. Notice what's not on the list: ordinary age. Sealed, dry, room-temperature ammunition routinely outlives its owner's interest in that caliber.
Cans are the storage system
Can combo listings pair bulk ammo with the sealed steel can it should live in — buy the storage with the ammo once.
See 9mm in a sealed ammo can →The rotation habit: first in, first out
Storage isn't a vault; it's a queue. Date every can or case with a marker when it arrives, shoot the oldest ammo first, and replace at the back of the line. This first-in-first-out habit costs nothing and quietly guarantees that nothing in your reserve is ever more than a few years old — which turns every debate about decades-long shelf life academic. It also gives you a continuous, free function check: because your range sessions consume the oldest inventory, any storage problem announces itself in a practice session rather than in a moment that matters. Pair rotation with a simple count — a note on each container of what's inside — and you always know what you actually have, which is half the battle in deciding when the next case purchase makes sense.
Defensive ammo: the stricter subset
Range reserve tolerates a lot; carry and home-defense ammunition deserves the strict version of every rule. Keep it in the original boxes inside the sealed can, rotate it on a schedule rather than "eventually" — shooting last year's carry load for practice and replacing it fresh is the standard pattern — and be ruthless about chamber-cycled rounds. A cartridge that's been repeatedly chambered and unloaded can suffer bullet setback, which raises pressure; retire frequently-cycled rounds to the practice pile instead of returning them to the top of the magazine indefinitely.
Buying storage and ammo in one move
If your reserve is outgrowing its containers, note that the cheapest time to buy storage is usually inside the ammo purchase itself. Bulk-plus-can combos deliver rounds already sealed in the military-style can they'll live in — gasket, desiccant-ready, stackable — which skips the repacking step entirely and typically beats buying cans separately. It's the rare purchase where the packaging is half the product. However the ammo arrives, the standard applies from day one: sealed, desiccant inside, dated on the lid, stored low and cool, and proven in your gun before it earns the label of reserve rather than inventory.
Frequently asked questions
How long does ammunition last in storage?
Stored cool, dry, and sealed, modern factory ammunition remains reliable for decades — surplus stored in sealed cans since the mid-20th century still fires. The enemies are humidity, temperature cycling, and oil contamination, not time itself.
Should I store ammo in the original boxes or loose in cans?
Either works inside a sealed can with desiccant. Original boxes add organization and protect tips; loose packing fits more per can. For defensive ammo, keep original boxes so lot numbers and load identity stay attached.
Is it bad to store ammo in a garage or attic?
Usually yes for attics and uninsulated garages — both swing hot and cold daily, and cycling drives condensation inside containers. A closet or interior room at stable household temperature beats any exterior space, even with sealed cans.