For responsible gun enthusiasts, proper ammunition storage goes hand-in-hand with safety and reliability. They want to know their ammo will perform flawlessly when it’s needed most. But how long can you leave that box of bullets on the shelf and expect it to last? Like many things in life, the answer is multifaceted. Below is a breakdown of the longevity of different types of ammo, essential storage tips to keep your rounds in tip-top shape, and signs of corrosion and damage that can lead to malfunctions and accuracy issues.

Understanding Shelf Life: It’s All About the Environment

While some might say ammunition lasts forever, that’s not quite true. The key factor affecting ammo shelf life is storage conditions. Ammunition is susceptible to environmental elements such as moisture, temperature changes, and sunlight. These elements can degrade propellant chemicals, corrode casings, and damage primers, leading to potential malfunctions, misfires, and accuracy issues.

The 10-Year Myth: Only A General Guideline

Many manufacturers provide a 10-year shelf life on their ammunition. This is a good starting point, but it’s more of a legal and liability measure than a strict expiration date. They know that the average shooter practices poor ammo storage habits. However, properly stored ammo can often last for decades.

Diving Deeper: Ammo-Specific Considerations
Even though storage is the most important factor in ammo shelf life, different types of ammo do have varying vulnerabilities to the environment. Here are the variations found in three standard types of ammo. We’ll begin by examining the variations found in three standard types of ammo. 

Centerfire Rifle and Pistol: These workhorses are tough and resilient. Brass casings offer good protection, and modern propellants are stable. With proper storage, you can expect the longest shelf life from centerfire ammo. 

Rimfire: This type of ammo design, where the primer is part of the rim, makes it more susceptible to moisture. As a result, the shelf life of rimfire ammo is often shorter than centerfire ammo when stored haphazardly. 

Shotgun Shells: Shotgun shells, like centerfire cartridges, have a long shelf life when stored correctly. When stored poorly, moisture can cause the cardboard wads to swell and primers to corrode. Metal shells offer additional protection, but humidity is still a serious threat. 

The Secret Weapon: Proper Storage Techniques

After understanding that proper storage is key, implementing the best practices listed below will maximize the shelf life of all types of ammo.

Control Temperature and Humidity: Keep ammunition in a climate-controlled environment with stable temperature and humidity levels to prevent the degradation of components. Avoid attics, garages, or anywhere with extreme temperature fluctuations. Also keep ammunition away from direct sunlight, as UV radiation can accelerate the aging process and degrade the quality of the cartridges. A basement or interior closet is ideal.  

Use Airtight Containers: Metal ammo cans are your best bet. They provide excellent protection against moisture, dust, and light. Plastic ammo boxes can work too but ensure they’re airtight. Also, consider adding desiccant packs to ammo cans. These moisture absorbers help regulate humidity and prevent corrosion. Last, remember that loose ammo is unhappy ammo. Fill any empty spaces with packing materials like foam or cardboard to prevent jostling during transport. Even better, leave ammo in its original packaging as much as possible.

Don’t Leave It Loaded: While it might be tempting to keep magazines loaded for quick access, avoid it for long-term storage. It’s recommended not to store ammo in a magazine for more than six months at a time. When a bullet is in a magazine, it’s more exposed to humidity and temperature changes, both of which are potentially damaging. Spring tension on the cartridge can also damage the bullet or case over time. Rotate your magazines regularly and unload them for storage.

First In, First Out: Treat your ammo like groceries by rotating stock. Use the oldest rounds first to ensure a constant flow of reliable ammunition. Label your containers with the caliber, type of ammo, and date of purchase. This makes it easy to identify what you have and helps with stock rotation. This is especially important for competitive shooters. For example, many rimfire competitors say they won’t use rimfire ammo that is over five years old for serious competition, just plinking.

Special Considerations: Different Ammo, Different Needs

While the core storage principles of storage remain the same, there are some nuances to consider for some unique types of ammunition.

Reloads: Hand-loaded ammunition requires extra care. Its shelf life depends on the quality of components and loading practices. Consult reloading manuals for specific recommendations.

Steel-Cased Ammo: Steel is more susceptible to rust compared to brass. Desiccant packs become even more important here. A light coat of gun oil on the exterior of the casings can provide additional protection.

Corrosive Ammo: This older surplus ammo often uses corrosive primers that leave behind nasty residues after firing. If you inherit a stash of corrosive ammo, be sure to clean your firearm meticulously after each use. When storing corrosive ammo, double down on moisture control to prevent further corrosion.

Black Powder: This type of primitive powder requires even stricter moisture control. Sealed containers and desiccant packs are essential. Black powder can also degrade over time, so be cautious with older powder.

Signs of Degraded Ammo: When to Say Goodbye

Even with proper storage, there’s always a chance ammo can degrade. Here’s what to look for before firing a potentially compromised round.

Visible Corrosion: Rust on steel casings or a greenish tint on brass casings indicates moisture damage. Rimfire ammunition that has not been stored correctly causes the grease lube to dry out and gives the lead a white, chalky look. While it will still likely fire, this may reduce the bullet’s accuracy because it needs the grease to lubricate the barrel. 

Damaged Ammo: Discard any ammo with cracks or splits in the casings. These can cause dangerous ruptures during firing. Bullets that are dented, bulged, or have a separated jacket also should not be used. Last, if the propellant inside the casing appears sticky or clumpy, it’s degraded and unsafe to use.

When in Doubt, Throw It Out: Safety is paramount. If you do test ammo with slight corrosion, do so slowly and carefully after wiping it down with a cloth. When the corrosion is so bad it won’t come off, throw it away. If a round won’t chamber in a bolt-action rifle, don’t shoot it. Never rapid-fire corrosive ammo in a semi-auto rifle. Barrel blockage from a squib can cause serious damage to your gun and lead to injury or death.

Wrap Up: Respect and Inspect Your Ammo
By understanding shelf-life variations of different types of ammunition and implementing proper storage practices, you can ensure your ammo stockpile remains reliable for years or even decades to come. Think of it as an investment in your protection, performance, and safety. Armed with the proper knowledge and care, your ammo will be ready whenever you need it, ready to perform flawlessly when the moment of truth arrives.

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