How to Store Ammo Long-Term: Temperature, Humidity and Containers
October 06, 2026 · BrassGrid
Short answer: keep ammunition cool, dry and at a steady temperature - roughly below 80°F (27°C) and under about 50% relative humidity - in a closed container, away from sunlight, heat sources and oils or solvents. Stored that way, modern factory ammunition commonly stays reliable for decades.
What actually damages ammunition?
- Moisture. Humidity corrodes cases and can reach the primer and powder. Green or white crust on brass is the first sign.
- Heat. High temperatures slowly break down powder and can change how a round performs. Attics, sheds and vehicles in summer are the usual culprits.
- Temperature swings. Warm days and cold nights make condensation form inside boxes and cans - steady beats merely cool.
- Oils and solvents. Penetrating oils and cleaning solvents can seep into primers. Keep cleaning supplies in a separate bag or bay.
- Handling damage. Rounds rattling loose in a can get dented cases and bullets pushed out of place. A pocket for every round stops that.
What conditions should you aim for?
| Factor | Aim for | Avoid |
|---|---|---|
| Temperature | Steady, roughly 50-80°F (10-27°C) | Attics, garages, vehicles, near heaters |
| Humidity | Below about 50% RH | Basements without a dehumidifier, bare concrete floors |
| Light | Dark - a closed case or cabinet | Direct sun through a window |
| Neighbors | Other dry storage | Solvents, oils, cleaning chemicals |
Which container is best?
There is no single best container - it depends on whether you are storing for years or grabbing ammo for the range.
| Container | Good at | Weak at |
|---|---|---|
| Original cardboard box | Labelled, free | Absorbs moisture, falls apart, rounds rattle |
| Gasketed steel or plastic ammo can | Keeping moisture out for years | Bulky; loose rounds jumble together |
| Fitted organizer case | One pocket per round, sorted by caliber, fast to count | Not airtight on its own |
Many shooters combine the two: rounds sorted into fitted cases, and the cases kept inside a sealed can or a closed cabinet with desiccant. Our cases are built in the case builder around exactly what you own - every round stands in its own pocket, so nothing rattles and a full row tells you the count at a glance.
Do you need desiccant?
If your storage spot is ever humid, yes. A few rechargeable silica gel packs in a sealed container keep the air dry, and a humidity indicator card tells you when to dry them out. Recharge them in a low oven following the maker's instructions.
Where in the house should ammo go?
An interior closet or cabinet in the living space is usually the most stable spot: it stays at room temperature year-round. Keep it off bare concrete floors (they wick moisture), out of reach of children, and locked where required by your local laws.
How long does ammunition last?
Factory ammunition has no fixed expiry date. Manufacturers generally quote ten years or more under good storage, and properly stored rounds decades older routinely fire normally. Rotate stock anyway - shoot the oldest first - and set aside anything with corrosion, dents, loose bullets or damaged primers. Ask your local range or police department how to dispose of it.
A note on 3D-printed cases and heat
Our cases are printed in PLA, which is rigid and accurate but starts to soften around 130-140°F (55-60°C). That is fine anywhere people live, but a car interior in summer can get hotter, so do not leave a printed case - or your ammunition - in a parked car.
Frequently asked questions
Does ammo expire?
No. Factory ammunition has no expiry date. Stored cool and dry it commonly lasts decades; discard rounds that show corrosion, dents or loose bullets.
Can I store ammo in the garage?
It is not ideal. Garages swing between hot and cold and are often humid, which causes condensation and corrosion. An interior closet or cabinet is more stable.
Is it OK to keep ammo in its original box?
For short-term storage yes, but cardboard absorbs moisture and wears out. For long-term storage, move rounds into a sealed container or fitted case with desiccant.
Should I use desiccant with ammo?
If the storage area is ever humid, yes. Rechargeable silica gel in a closed container keeps humidity down; a humidity card shows when to recharge it.
Can I leave ammo in a hot car?
Avoid it. Heat degrades powder over time, and a parked car in summer can also soften plastic and 3D-printed cases.