How To Store Ammunition Long Term: The Ultimate Preservation Guide

Proper ammunition long-term storage hinges on controlling three primary environmental factors: relative humidity, ambient temperature stability, and exposure to airborne contaminants. By combining military-grade surplus metal containers, food-grade desiccants, and climate-controlled storage locations, reloaders and preparedness practitioners can preserve reliable primer ignition and powder stability for decades.

Environmental Controls & Equipment Checklist

Preserving modern centerfire and rimfire cartridges requires a strict adherence to chemical stabilization principles. Smokeless powder and priming compounds degrade prematurely when exposed to extreme thermal cycles and moisture, making proper container selection and site preparation non-negotiable.

• Essential Gear & Materials:

  
  
  
  • Genuine USGI .50 caliber or Fat 50 steel ammo cans equipped with intact, pliable rubber lid gaskets.
  • Silica gel desiccant packs (indicating or non-indicating) calculated at roughly 10 grams of desiccant per 100 cubic inches of container volume.
  • Heavy-duty vacuum-sealing bags and a chamber vacuum sealer (optional secondary moisture barrier).
  • Digital hygrometers and maximum/minimum thermometers for storage area monitoring.
  • Non-petroleum preserving oil and lint-free microfiber cloths for brass wiping.

• Prerequisite Knowledge & Standards:

  
  
  
  • Ideal storage parameters dictate a stable ambient temperature between 55°F and 70°F (13°C to 21°C) with a relative humidity level consistently below 50%.
  • Avoid storing ammunition in concrete-floored basements or uninsulated attics where condensation cycles accelerate brass corrosion and powder breakdown.

• Execution Scope & Benchmarks:

  
  
  
  • Setup time requires approximately 1 to 2 hours for inspecting, cleaning, and packing 1,000 rounds.
  • Initial material investment ranges from fifty to two hundred dollars depending on container quantity and desiccant volume.

Step-by-Step Ammunition Preservation Workflow

Step 1: Inspect and Prepare the Cartridges

Examine your ammunition inventory meticulously before placing any rounds into long-term containers. Sort the cartridges by caliber, lot number, and manufacturer to ensure consistent performance tracking over the coming decades. Discard any rounds showing deep scratches, split necks, severe verdigris corrosion on the casing, or pushed-in primers. Wipe down clean brass casings with a lightly oiled cloth to remove acidic fingerprint residues left behind during handling, then buff them completely dry.

Warning: Never use commercial solvent cleaners or harsh chemical degreasers on loaded ammunition, as capillary action can draw liquids past the bullet crimp or primer seal, contaminating the propellant and rendering the round a dud.

Step 2: Select and Test Storage Containers

Acquire military-surplus steel ammunition cans featuring functional rubber gaskets. Inspect the perimeter seal closely; if the rubber feels dry, cracked, or brittle, replace the lid or the gasket entirely. Perform a simple closure test by placing a strip of standard printer paper across the lip of the can, latching the lid, and attempting to pull the paper free. If the paper slides out without noticeable resistance, the seal is compromised and air will freely exchange with the outside environment.

Pro-Tip: Smear a very thin, nearly invisible layer of pure silicone grease onto the rubber ammo can gasket to restore suppleness and create an airtight hermetic seal.

Step 3: Layer Desiccants and Pack Containers

Arrange the ammunition inside the steel can systematically, either left loose to maximize volumetric efficiency or kept inside original factory packaging if space permits. Place indicating silica gel packets at the bottom, middle, and top of the container to ensure uniform moisture absorption throughout the stack. Do not rely entirely on cardboard boxes for long-term storage, as cardboard acts as a sponge for ambient moisture and introduces chemical acids directly to the brass surface.

Step 4: Seal and Monitor the Storage Environment

Latch the steel container securely and place it on elevated shelving rather than directly against a concrete floor, which acts as a thermal sink and draws moisture upwards. Position a digital hygrometer inside the storage room to track baseline humidity and temperature fluctuations. Check the color-changing indicator window on your desiccant packs every six to twelve months to ensure internal humidity remains safely below critical thresholds.

Troubleshooting Ammunition Degradation Issues

Surface Verdigris and Copper Tarnish

• Root Cause: Direct contact with acidic skin oils or prolonged exposure to high relative humidity interacting with the copper-zinc alloy casing.
• Actionable Fix: Inspect the casing walls for pitting. If the corrosion is purely surface-level tarnish, polish it away gently with a dry microfiber cloth, wipe clean, and repackage the rounds with fresh silica desiccant inside a sealed steel can. Discard any rounds with deep pitting that compromises structural integrity.

Failed Primer Ignition (Hangfires or Duds)

• Root Cause: Contamination of the priming compound caused by liquid oil migration past the primer-pocket seal during improper cleaning.
• Actionable Fix: Immediately segregate the affected lot of ammunition. Inspect your handling procedures to ensure lubricants are never applied directly to loaded cartridges. For safety, dispose of confirmed contaminated rounds through local hazardous waste facilities or authorized shooting range disposal protocols.

Musty Odor and Box Decomposition

• Root Cause: Storing ammunition in cardboard packaging within a humid, unventilated subterranean space.
• Actionable Fix: Discard all damp and degraded cardboard packaging immediately. Clean the sound ammunition casings with a dry cloth, transfer them into sterile plastic ammo trays or directly into military steel cans, and upgrade your storage area with a dedicated room dehumidifier.

Frequently Asked Questions

How long does ammunition actually last when stored properly?

When kept in cool, dark, and dry conditions with stable temperatures between 55°F and 70°F, factory-loaded centerfire ammunition can remain fully functional for 40 to 50 years or even longer. Military surplus ammunition packaged in sealed metal containers has historically proven reliable after 70 years in storage.

Can I store ammunition in a standard kitchen refrigerator or freezer?

No, standard household refrigerators and freezers are poor choices for long-term ammunition storage. Refrigeration units cycle humidity levels wildly and introduce condensation onto cold metal surfaces whenever the door is opened, accelerating corrosion and chemical breakdown.

Is it safe to store loaded magazines loaded for long periods?

Modern magazine springs do not degrade simply from being compressed under tension; rather, they wear out from the continuous cycle of loading and unloading. You can safely store quality steel or aluminum magazines loaded for years, provided the storage environment remains dry and free of corrosive agents.

How do I know if my desiccant packs are exhausted?

Most standard silica gel packets utilize an indicating dye that shifts color—typically from bright blue or orange to pale pink or green—when they reach moisture saturation thresholds. Once the color shifts, you can reactivate reusable packs by baking them in a standard oven at low heat according to manufacturer instructions.

Protect your ammunition investment with military-grade surplus containers and precise environmental controls today. Start organizing your stockpile now to ensure peak ballistic performance for decades to come.