How Long Is Ammo Good For? How Shelf Life of Ammo is Affected by Moisture, Temperature and More

Most of us hunters or firearm enthusiasts have a good bit of ammo laying around, and some of it may be fairly old, but just how long is that old ammo good for? Plenty of enthusiasts have asked this question and as it turns out there are many variables at play when it comes to ammo storage. Most manufacturers will tell you that your ammo is only good for 10 years, but we also have ammo from world war two that is still going strong, so what is the real answer? Well to find out, let’s dive into ammo and all the things that make it tick.

How Moisture Ruins Ammo

One of the most important things about ammo, especially old ammo, is moisture. Your ammo has to absolutely stay dry. I am sure I am not the only one that ran some 22 ammo through the washer as a kid to test this theory. Obviously, after the ammo was soaked in water it had a lot of trouble firing and if it did fire, it often did not cycle through my action. 

One thing that most people do not think about is the moisture in the air. Depending on where you live, if you store ammo on a shelf in a non-air-conditioned garage, the moisture can get to it and make the powder inside useless. That is why a lot of enthusiasts use ammo cans or safes. If you store your ammo in an ammo can or another type of storage that restricts airflow, then the moisture in the air can not mess with your ammo and that ammo with last much longer than its counterpart that is exposed to the ambient air.

Contrary to popular belief, ammo is not air-tight. Although the fit between the projectile and casing may seem really tight to the naked eye, it is not perfect and will definitely let air and moisture through. If you do not already, I highly suggest storing your ammo in an air-tight safe or at least an ammo can.

Effects of Temperature Fluctuations on Ammo Reliability

Most of us have ammo sitting out in the garage exposed to the elements, but did you know that leaving that ammo out during the year and letting it experience winter and summer temperatures can have a large effect on its reliability? 

High and low temperatures have a large effect on not only the powder of old ammo but also the primers of all ammo. This effect can make cartridges in the same box act drastically different. Some of your rounds may barely get enough power to push the bullet out of the barrel, while other rounds will make the cartridges have twice the power as before and sound like cannons. 

Really the bottom line is highly volatile temperatures will make ammo of all kinds also act with high volatility. If it is at all possible you should store your ammo in a climate-controlled area so that you can be one hundred percent positive that your ammo is not fluctuating in temperature and also not being exposed to high humidity.

First in First Out | a Good Practice With Ammo

One thing that will help you preserve your ammo reliability is marking your ammo. By marking your ammo I mean writing on the box when you bought the ammo so that you roughly know how old the ammo is. Obviously, the ammo could have been sitting on the shelf at the gun store for a considerable amount of time but you have no way of knowing that.

What this practice does is makes sure that when you go looking for ammo, you first pull out the ammo you bought in 2019 instead of the ammo you bought last week because it was on sale. What this does is makes sure that you pull the oldest ammo out when you need to use it. This practice makes sure that you do not ignore a set of ammo for years on end and wind up giving that ammo a higher chance of going bad because you naturally chose to shoot the closest ammo to you, which was the newest ammo.

They use this principle all over the food industry where companies try their best to eliminate waste by making sure that their employees do not accidentally ignore the older product. This leads to less waste overall. We can use the same principles when dealing with ammo.  

Old Ammo Vs Modern Ammo

If you are buying brand new ammo and are worried about storing it, I would say that you do not have much to worry about. Especially if you store it in a climate-controlled area. Although if you have gotten your hands on some older ammo, you should be more considerate about how you store it.

The fact that we have come such a long way since black powder and steel casings lets us be a little laxer with modern ammo, but if you are rocking world war two era ammo or ammo that is a couple of decades old, you need to store it in optimal conditions. 

Personally, I would store it in an ammo can inside of a safe that is inside of a climate-controlled room. Some people may say this is overkill and that they have had world war two ammo stored in the open air of their garage for decades, but when they pull it out and load it in a clip we will definitely be able to tell who stored their ammo better.

The Bottom Line

So we can really keep ammo for multiple decades even though most manufactures will only tell you to keep it for 10 years. They say this so that they do not have any liability when it comes to someone trying to fire 50-year-old ammo, and they also want to sell you new ammo. However, if you store your ammo correctly, you should not have a problem with hanging on to it for a really long time.

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