PART 1: SHELF LIFE — THE MOST COMMON AMMO MYTHS

Ammo Myth #1: “Ammunition expires after 10 years”

Verdict: FALSE.

This is the most persistent of all ammo myths, and like most ammo myths it exists for a very simple reason: ammunition manufacturers say so.

Most of them will tell you their ammo has a ten-year shelf life. But that number isn’t a scientific finding — it’s a liability position. No manufacturer wants to be on the hook for a round that fails after two decades in someone’s damp shed. (And, in fairness, they’d also quite like you to buy more ammo.)

What actually happens

Ammunition has no expiry date. It has storage conditions.

Doug Wicklund, Senior Curator at the NRA Museums, put it plainly: he has fired factory loads from the 1870s that “went bang and hit the target accurately.”

An NRA writer described pulling out his late father’s surplus .303 British — ammunition somewhere between 75 and 100 years old — and firing it without drama. Military surplus from the 1940s and 1950s is still being shot every weekend, all over the world, right now.

So how long does it last?

It depends almost entirely on where you kept it:

The takeaway: age isn’t the enemy. Environment is. A five-year-old box that lived in a hot garage is in worse shape than a fifty-year-old box that lived in a sealed can in a cupboard.

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Ammo Myth #2: “Old ammo is dangerous”

Verdict: MOSTLY FALSE — one of the ammo myths with a grain of truth, but with one real exception.

Here’s the reassuring part: when ammunition finally gives up, it usually does so by not working, not by exploding.

The most common failures of old ammo are:

• A misfire — you pull the trigger, nothing happens. Annoying. Not dangerous (if you handle it correctly).
• A hangfire — a delayed ignition. The round fires a fraction of a second late. This one deserves respect. If a round fails to fire, keep the gun pointed downrange for a full 30 seconds before you open the action. A hangfire that goes off while you’re unloading is a genuinely bad day.
• Weak or inconsistent velocity — degraded powder produces less pressure.

The one that genuinely matters: the squib

A squib load is when the powder is so degraded that it produces just enough pressure to push the bullet into the barrel — but not out of it.

The bullet lodges. The gun feels and sounds wrong — a weak “pop” instead of a bang, less recoil than expected.

If you fire the next round into an obstructed barrel, the barrel can burst. This is how people lose fingers.

🚨 The rule that keeps you safe

If a shot ever sounds or feels weak — STOP. Unload. Check the barrel.

Run a cleaning rod down it. If it doesn’t pass all the way through, you have a squib and a trip to the gunsmith. If it does, carry on.

That single habit protects you from essentially every real danger old ammunition presents.

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Ammo Myth #3: “If it looks fine, it is fine”

Verdict: MOSTLY TRUE — a rare entry on our ammo myths list that’s mostly right — with a neat trick for the rest.

Visual inspection catches the overwhelming majority of problems (we’ll cover exactly what to look for in Part 4).

But powder degradation is invisible — it’s happening inside a sealed brass case where you can’t see it.

The armorer’s drop test

Here’s an old trick from military armorers, and it costs nothing:

Drop a cartridge from about six inches onto a hard surface and listen.

• A clear, bright “ring” suggests healthy, dense powder.
• A dull “thud” can indicate powder breakdown or moisture inside.

Is it 100% reliable? No. It’s a rough indicator, not a laboratory test. But it’s free, it takes two seconds, and it’s a useful nudge toward “maybe test-fire a few of these before trusting the batch.”

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PART 2: FIRE AND HEAT — THE MOST DANGEROUS AMMO MYTHS

Ammo Myth #4: “Ammunition explodes in a house fire”

Verdict: SPECTACULARLY FALSE — the king of all ammo myths. And we know this because SAAMI set an enormous quantity of ammunition on fire to find out.

This is the myth Hollywood built — the most cinematic of all ammo myths — and it’s worth killing properly — not least because it puts firefighters at unnecessary risk when they hesitate to enter a home with ammunition in it.

What SAAMI actually did

In cooperation with the International Association of Fire Chiefs, SAAMI ran an extraordinary series of tests. They subjected hundreds of thousands of rounds — figures cited range from 400,000 to nearly one million rounds across ten different test regimes — to conditions including:

• Open bonfires, both packaged and unpackaged
• 65-foot drops
• Attacks with blasting caps
• Being shot with other bullets
• Forklift impacts
• Being crushed and ground by a bulldozer
• Simulated retail store fires and truck trailer fires

They tested rifle and pistol cartridges up to .50 caliber, and shotshells up to 8 gauge.

What they found

A cartridge outside a gun cannot generate meaningful bullet velocity.

Here’s the physics, and it’s beautifully simple. To push a bullet fast, the expanding gas has to be tightly confined — which is exactly what a gun chamber does. Outside a chamber, the brass case is the weakest thing in the assembly. So when the powder ignites, the case simply bursts open and the gas escapes in every direction.

SAAMI’s own conclusion is worth reading twice:

Bullets and shot are not projected at velocities higher than you could throw them by hand.

In their open-burn tests, relatively few projectiles were found more than 40–50 feet from the fire. The cases burst and bits of brass flew about — but “usually not with force enough to be dangerous to life.“

And that alarming “whizzing” sound reported in newspaper accounts of gun-shop fires? It’s the primers, not the bullets. The popping and banging is loud. It is not lethal.

The official position

“Tests and years of experience indicate that there is no appreciable hazard in storing any amount of loaded small arms ammunition in a dwelling.”

Firefighters in standard turnout gear are safe working a fire containing ammunition. In fact, SAAMI notes that the aerosol cans and propane cylinders sitting on the same shelf in a sporting goods store are far more dangerous than the ammunition.

⚠️ The one genuine exception

A loaded gun in a fire is a different matter entirely.

If a cartridge is in the chamber, it is confined — and it will launch the bullet at full velocity, in whatever direction the barrel is pointing.

Store ammunition and firearms unloaded. That’s the actual safety lesson buried under this myth.

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Ammo Myth #5: “Ammo will cook off in a hot car”

Verdict: FALSE. This is one of the ammo myths where the numbers aren’t even close.

Every summer this one of the most repeated ammo myths resurfaces, and every summer the physics stays the same.

The temperature it takes

• Primers (modern lead styphnate compound) have a cook-off range of roughly 250–330°F, according to US Naval ordnance testing. They can sit at those temperatures for an hour without self-igniting.
• Smokeless powder (nitrocellulose) ignites somewhere around 320–338°F. Testing on 7.62mm cartridges found the propellant didn’t cook off until chamber temperatures hit roughly 304°F — and even then only with sustained, direct heat and confinement.
• Lead melts at 621°F.

The temperature a car actually reaches

Arizona State University measured this properly. Cars parked in direct summer sun:

The hottest surface in a car in the Arizona sun is about 157°F. A primer needs at least 250°F.

That’s roughly a 90-degree margin of safety — and that’s on a dashboard, in Phoenix, in direct sun. Even Death Valley’s all-time record of 134°F doesn’t come close.

Your ammunition is not going to explode in your car. Full stop.

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Ammo Myth #6: “So heat doesn’t matter”

Verdict: FALSE — and of all the ammo myths, this is the one that actually costs people money.

Here’s where the internet gets it backwards, and where the ammo myths do real harm. Everyone argues about whether ammo will explode in a hot car (it won’t), and almost nobody talks about what heat actually does — which is far more likely to affect you.

Heat kills ammo slowly

The main ingredient in smokeless powder is nitrocellulose, and it is inherently unstable. It’s slowly breaking down from the day it’s made.

Manufacturers add chemical stabilizers to slow this decay. But those stabilizers get consumed over time — and heat accelerates the process dramatically. Once the stabilizers are exhausted, degradation speeds up sharply.

Modern ammunition is engineered to tolerate roughly -40°F to 150°F. A car in summer sits right at the top of that range, day after day, cycling between scorching afternoons and cool nights. That repeated thermal stress burns through the stabilizers far faster than steady, cool storage.

What degraded powder actually does

Per SAAMI, extended high-temperature exposure can cause:

• Lower pressures → weak velocity, or a squib
• Incomplete powder burn
• Failure to fire
• And in some cases, counterintuitively, increased pressure — raising the risk of a dangerous overpressure event

SAAMI explicitly advises against leaving ammunition in a vehicle or trunk on a hot day.

🚗 The practical rule

One afternoon in a hot car will not hurt your ammo. A whole summer in your truck absolutely will.

If you must transport ammo in heat:

• Keep it in original packaging or a sealed ammo can (insulation + blocks sunlight)
• Put it on the floor of the cabin, not the dashboard or rear shelf
• For long trips, an insulated cooler genuinely helps
• Bring it inside when you get home

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PART 3: COLD AND FREEZING AMMO MYTHS

Ammo Myth #7: “Freezing ruins ammunition”

Verdict: FALSE. Of all the ammo myths, this is the one hunters most need to understand. Cold doesn’t damage ammo — but it definitely changes how it shoots.

Cold doesn’t hurt it — but it slows it down

Powder burns more slowly when it’s cold. Slower burn means less chamber pressure, which means less velocity.

Norma ran exactly this test with .30-06 hunting ammunition and a 22-inch barrel. They stored three boxes overnight at three different temperatures, then chronographed them:

The point of impact shifted down and to the right — progressively further with each drop in temperature.

Sierra ballistician Tommy Todd found the same effect from the other direction: heated .308 rounds hit 2,596 fps, cooled ones only 2,451 fps — a 145 fps swing, enough to produce a visible point-of-impact shift at 200 yards.

It’s worse than you think at distance

Ballistician Bryan Litz notes that for every 20°F drop in temperature, air density rises about 2% — which slows the bullet further and steepens its arc.

The US Army puts a hard number on it:

“If the last time your weapon was zeroed the temperature was 90°F and you’re now in freezing temperatures, your ammo could impact the target nine inches low at 300 meters.”

Nine inches. On a deer. That’s a wounded animal instead of a clean harvest.

⚠️ The real cold-weather danger: condensation

Here’s the part nobody warns you about, and it’s the thing that will actually damage your ammunition.

When cold ammo meets warm air, moisture condenses on it — exactly like a cold drink sweating on a summer day. That moisture can seep into primers and cases.

So the mistake isn’t storing ammo somewhere cold. It’s storing it somewhere cold and then repeatedly bringing it somewhere warm.

Practical rules for cold weather:

• Let ammo acclimate gradually — don’t yo-yo it between extremes
• Zero your rifle in the conditions you’ll hunt in. An indoor summer zero is a lie in December.
• On a hunt, keep spare rounds in an inside pocket — body heat keeps them consistent
• If you’re serious about precision, know your load’s temperature sensitivity

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PART 4: CORROSION — THE AMMO MYTHS THAT COST YOU A GUN

This is the part that could actually save your gun

Ammo Myth #8: “Tarnished ammo is unsafe”

Verdict: FALSE. And this one causes people to bin perfectly good ammunition.

This is one of the ammo myths that causes real waste. Brass tarnishes. It’s what brass does. Look at any old brass doorknob.

Dull, darkened, brownish, or slightly discoloured brass is COSMETIC. It means the case surface has oxidised. It tells you nothing about the powder or primer inside.

Experienced shooters routinely fire ammunition that looks far worse than yours. Surplus rounds that came out of a can looking thoroughly unloved go bang perfectly well every day.

If the case is dull but smooth, unpitted, undented, with a clean primer — it’s fine. You can wipe it with a dry cloth if it bothers you.

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Ammo Myth #9: “Green corrosion? Just clean it off”

Verdict: DANGEROUSLY FALSE. Of all the ammo myths in this guide, this is the one that could actually hurt you.

Tarnish and corrosion are not the same thing

Verdigris is that green (sometimes blue-green, sometimes white and powdery) crust that forms on brass and copper exposed to moisture, sweat, or acidic contact. It’s the same stuff that turns copper church roofs green.

And here’s the critical point: it isn’t sitting on the brass. It’s brass that has been eaten away.

That green crust is the product of your case being chemically consumed. Underneath it, you’ll frequently find pitting — actual craters in the metal.

Why cleaning it doesn’t fix it

You can scrub the green off with alcohol, vinegar, or a cloth. The brass it consumed does not come back.

Worse: the moisture that caused the corrosion has probably also gotten inside the case — where it degrades the powder and can kill the primer.

The failure modes

• Case head separation — the case head is the thickest, most pressure-bearing part of the cartridge. Corrode it and it can split or blow out when fired. This is the one degradation mode that is genuinely, seriously dangerous rather than merely unreliable.
• Squib loads — from powder ruined by the moisture that came with the corrosion
• Chamber jet-cutting — one shooter fired cleaned-up but corroded surplus and reported that the compromised case heads let hot gas escape and cut grooves into his rifle’s chamber. New barrel required.
• Rounds sticking — verdigris can literally glue a cartridge into a chamber or magazine

🚨 The rule

Dull and dark = cosmetic. Fire it. Green, white, fuzzy, crusty, or pitted = DON’T. Dispose of it.

Test it if you’re unsure: press a sharp point (a centre punch works) on the corroded spot, then on clean brass nearby. If the corroded area indents more deeply, the metal is compromised. Bin it.

A box of ammo costs $25. A barrel costs $400. Your hand is priceless.

💡 Why your carry ammo goes green

Noticed verdigris on the rounds in your carry gun but not on the box in your safe? That’s your sweat. Body salt and acid are brutal on brass.

Two fixes: rotate your carry ammo (see Myth 12), and consider nickel-plated cases, which resist corrosion far better than bare brass. It’s not a coincidence that most premium defensive ammunition uses nickel-plated cases.

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PART 5: HANDLING AND STORAGE AMMO MYTHS

Ammo Myth #10: “A dropped round can go off”

Verdict: FALSE.

This is one of those ammo myths that sounds plausible until you see the test data. A primer needs a sharp, focused impact from a firing pin to ignite. Landing flat on a floor doesn’t come close to replicating that.

Remember SAAMI’s testing: they dropped ammunition 65 feet. They hit it with forklifts. They ran it over with a bulldozer. They shot it with other bullets. They set off blasting caps next to it.

If you drop a cartridge on the range, pick it up. It’s fine.

(Pick it up carefully all the same — good habits are good habits.)

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Ammo Myth #11: “Leaving magazines loaded wears out the springs”

Verdict: FALSE.

Few ammo myths are as stubborn as this one. Springs wear from cycling, not from compression.

A spring held at a constant compression sits well within its elastic limit and doesn’t meaningfully weaken. What wears a magazine spring out is being compressed and released thousands of times.

Magazines left loaded for years still function. Police and military armouries rely on this fact.

Fatigue comes from use, not from waiting. Load your magazines and stop worrying.

(The related myth — “downloading by one round saves the spring” — is likewise unnecessary, though it’s harmless if it makes you feel better.)

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Ammo Myth #12: “Carry ammo lasts forever”

Verdict: FALSE — and of all the ammo myths here, this one matters most.

This is the one entry on our list of ammo myths that could cost you when it matters most. The ammunition in your safe is in a stable, dark, dry environment. The ammunition in your carry gun is riding on your body.

That means it’s absorbing:

• Body heat — day in, day out
• Sweat — salty, acidic, brutal on brass (this is why carry ammo goes green first)
• Humidity — from your body and the outside air
• Friction and handling — every time you load and unload

And then there’s bullet setback

Every time you chamber a round, the bullet can be pushed slightly deeper into the case.

Chamber the same round repeatedly — as people do who unload their carry gun every night — and that setback accumulates. A bullet seated deeper reduces case volume, which raises chamber pressure. In extreme cases, dangerously so.

Never re-chamber the same round over and over. Rotate which cartridge goes on top.

🎯 The 12-month rule

Replace your defensive carry ammunition every 12 months.

Yes, it feels wasteful. Run the numbers and it isn’t:

• A box of 50 premium defensive rounds: roughly $25–35
• One box per year, per carry gun
• That’s one range session’s worth of ammo — annually

If you carry daily, you are trusting your life to that ammunition. Thirty dollars a year is the cheapest insurance you will ever buy.

And the old box isn’t wasted — shoot it at the range. You should be function-testing your carry load anyway.

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Ammo Myth #13: “Ammo in a magazine is fine indefinitely”

Verdict: PARTLY FALSE — one of the few ammo myths on this list with real nuance.

The spring is fine (see Myth 11). The ammo is the issue.

Loose in a magazine, cartridges are exposed to air, humidity, and handling in a way that boxed ammo isn’t. General guidance is to avoid leaving ammunition sitting in a magazine for more than about six months in a normal climate — less if it’s humid.

For range magazines, this hardly matters. For a home-defense gun that sits loaded for years, it’s worth periodically shooting and replacing the contents.

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PART 6: TWO MORE AMMO MYTHS WORTH KILLING

Ammo Myth #14: “Steel-cased ammo will destroy your barrel”

Verdict: OVERBLOWN. This is one of the ammo myths that’s half-true.

Steel cases are softer than your barrel steel. They don’t scour it out.

What’s actually true:

• Steel cases don’t obturate (expand to seal) as well as brass, which can let more fouling past — meaning more cleaning
• Some steel-cased ammo uses bi-metal jackets, which can accelerate throat wear over very high round counts
• Many indoor ranges ban it — because it’s magnetic and hard to sweep, and because they want the brass
• It’s not reloadable

For casual high-volume plinking in a rifle you’re not precious about, steel case is fine. For match rifles, or if you reload, stick to brass.

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Ammo Myth #15: “.22 LR lasts as long as centerfire”

Verdict: FALSE — one of the ammo myths that genuinely surprises people.

Rimfire is the most fragile ammunition you own.

In a centerfire cartridge, the primer is a separate, sealed component pressed into the case head. In rimfire, the priming compound is smeared inside the rim of the case itself — a far less protected arrangement.

That makes .22 LR more vulnerable to moisture and generally less durable in long-term storage than centerfire ammunition.

It still lasts a long time when stored well. But if you’re stockpiling, give your rimfire the best storage conditions you have — and don’t assume that fifty-year-old brick of .22 will perform like fifty-year-old .30-06.

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So What SHOULD You Actually Worry About?

We’ve spent a lot of words debunking ammo myths and things that won’t hurt you. Here’s the short list of things that will.

🚩 The genuine red flags — do NOT fire these

When in doubt, throw it out. No box of ammunition is worth a destroyed firearm or an injured hand.

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How to Store Ammunition Properly

Everything above comes down to three variables. Get these right and your ammunition will outlive you.

1. Humidity is enemy number one

• Target: 30–50% relative humidity
• Above 60% → degradation accelerates
• Above 70% → corrosion can begin within months
• A digital hygrometer costs under $15. Buy one. Put it where your ammo lives. Stop guessing.
• Use silica gel desiccant packs in sealed containers, and replace them every 6–12 months

2. Temperature: cool and, above all, STABLE

• Ideal: around 60–70°F
• What matters most is stability. Wild swings drive condensation and burn through powder stabilizers.
• ❌ Attics (bake in summer)
• ❌ Garages and sheds (no climate control)
• ❌ Damp basements (humidity)
• ❌ Car trunks (the worst of all worlds)
• ✅ A closet inside your climate-controlled house. Genuinely, that’s the answer. The best ammo storage is boring.

3. Seal it

• Military-style metal ammo cans with rubber gaskets are the gold standard — airtight, cheap, stackable, and they last forever
• Keep ammo in its original boxes inside the can (organisation + protection)
• Never store ammo near solvents or oils. Both can penetrate a case and kill the powder. This means don’t store ammo in the same sealed container as your cleaning kit.
• Handle it minimally — the oils and salt on your hands accelerate corrosion

4. Rotate: first in, first out

• Label containers with the purchase date. Sharpie on masking tape. Takes ten seconds.
• Shoot the oldest ammo first.
• Ammo that’s been out to the range and back gets used before the sealed stuff in storage.

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How to Dispose of Bad Ammunition

If you’ve decided a batch is compromised, do not throw it in the household bin. And please don’t try to burn it.

Your options:

1. Your local police department — many run disposal programs, or will take it. Call first.
2. A hazardous waste collection event — ammunition is usually accepted.
3. Many shooting ranges will take unwanted ammunition for disposal.
4. A licensed gun shop or gunsmith — many will dispose of it for you.

(Experienced reloaders sometimes pull bullets and separate components. If you don’t already know how to do that safely, this is not the time to learn.)

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The Bottom Line

Most ammo myths exist because ammunition looks dangerous. It’s got the word “explosive” hovering around it, so people assume the worst.

But the reality behind the ammo myths is that modern ammunition is remarkably stable and remarkably durable.

• It won’t blow up your house in a fire.
• It won’t cook off in your car.
• It won’t be ruined by a cold night.
• It doesn’t expire on a schedule.
• Dropping it is fine. Loaded magazines are fine. Tarnish is fine.

What ammunition genuinely hates is moisture, heat, and time — in that order.

Keep it cool, dry, sealed, and rotated, inspect it before you shoot it, stop immediately if a shot sounds weak, and never fire anything with green corrosion on it.

Do that, and the box you buy today will still be shooting straight in thirty years.

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Stock Up — and Store It Right

Now that you know your ammunition will genuinely last decades when stored properly, buying in bulk stops being a gamble and starts being smart economics. Prices fluctuate; well-stored ammunition doesn’t.

Browse our full range and buy with confidence:

Rifle: 5.56 NATO · .223 Remington · .308 Winchester · 6.5 Creedmoor

Handgun: 9mm · .45 ACP · .380 ACP · .38 Special

Rimfire: .22 LR

And if you’re carrying daily — this is your annual reminder. Replace your defensive ammunition. It’s the cheapest insurance you’ll ever buy.

This article is general educational information, not professional safety advice. Always follow your firearm manufacturer’s guidance and applicable federal, state and local laws. If you are ever unsure whether ammunition is safe to fire, do not fire it — consult a qualified gunsmith. Dispose of suspect ammunition through proper channels; never place it in household waste.

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Frequently Asked Questions

Does ammo expire? Not on a schedule. Manufacturers cite ten years for liability reasons, but properly stored ammunition reliably lasts 20–50+ years. People have successfully fired ammunition made in the 1870s. Storage conditions matter far more than age.

Can ammo explode in a fire? Not in the way films suggest. SAAMI burned hundreds of thousands of rounds and found that outside a gun chamber, bullets are not projected faster than you could throw them by hand. The exception is a loaded firearm — a round in a chamber is confined and will fire at full velocity.

Will ammo go off in a hot car? No. Primers need roughly 250–330°F to cook off. The hottest surface in a car in direct Arizona sun averages about 157°F. However, repeated heat exposure does degrade the powder over time — so don’t store ammo in your vehicle long-term.

Can you freeze ammunition? Freezing won’t damage it, but cold slows the powder burn, reducing velocity — a freezer-stored .30-06 lost about 92 fps in testing. The real risk is condensation when cold ammo meets warm air.

Is tarnished ammo safe to shoot? Dull, dark tarnish is cosmetic — yes, it’s safe. But green, white, fuzzy or crusty corrosion (verdigris) means the brass has been chemically eaten away. Do not fire it, and don’t just clean it off — the damage underneath is real.

How often should I replace my carry ammo? Every 12 months. Body heat, sweat and humidity degrade it, and repeated chambering causes bullet setback, which raises pressure. One box a year is trivial insurance.

Does leaving magazines loaded wear out the springs? No. Springs wear from cycling, not from static compression. Magazines left loaded for years work fine.

What’s the ideal way to store ammunition? Cool (60–70°F), dry (30–50% humidity), stable, and sealed. A closet inside your climate-controlled home, in gasketed ammo cans with desiccant packs, labelled with purchase dates. Not the attic, garage, basement or car.

What is a squib load? A round with insufficient powder to push the bullet out of the barrel, leaving it lodged inside. Firing the next round into an obstructed barrel can burst it. If a shot ever sounds weak — stop, unload, and check the barrel.

how long does ammo last