I generally follow his precepts, with one exception. I keep my ammo in climate controlled environments. That helps me not have to worry about temperature or humidity issues. For me, long term means that I bought the ammo within the last 30 years. Some people have been storing it for a lot longer than that.
Without further ado, here's Birddog's article.
*LONG TERM AMMUNITION STORAGE*
There has been much debate on what is the best way for long term storage of ammo, and while I can’t say it’s wrong to place your ammo in a bucket and suck out all the air and replace it with nitrogen I can say it is a waste of valuable resources.
O.K. if you plan being cryogenically frozen for hundreds of years then maybe. The rest of us just need to know what is the best way to properly store ammo so that it doesn’t degrade over a period of time and that it functions as designed when put into use.
Now. I need to give you some background on how and for what condition ammo is built. Military cartridges are designed so that they can withstand storage temperatures from minus 65 degrees F. to 122 F. So as long as you don’t keep them in an oven you’re fine. They’re made for soldiers to use in battlefield conditions under the most horrible conditions conceivable and still function.
The manufactures (OLIN, Winchester, Remington Etc.) know this and they also know they will lose a big fat Govt contract if they don’t pass this criteria. Here is one for you, the same folks that make 5.56mm make the exact same cartridge and call it a .223 ,change the label and sell it civilian. (Just a note: there are actually some differences, primarily in terms of pressure. Most people don’t know or care about these.)
Same with 308 (7.62 NATO). (Same note above applies)
So now you know that there is hardly any difference between civilian and military ammunition manufacturing. Let’s get down to storage.
Shelf life refers to how long an item can remain in storage and still be functional. Well, all military small arms have an indefinite shelf life. This means as long as it is properly stored it will never go bad. (I’ve fired military surplus from the 1930’s with no trouble. I have read of people firing ammo from the Spanish American War, with no ill effects.)
Service life refers to how long a item can remain in a operating configuration and still be functional. Small arms ammo should be good from anywhere from 6 months to 18 months before you need inspect it. If the ammo has some corrosion on it take some copper wool or steel wool and take it off then it’s good to go unless it is to the stage of pitting, then get rid of it.
Now, most ammo comes in a wooden outer container with metal inner packs that holds the ammo. We store it on at least two inches of dunnage to keep off the floor. It is inspected every five years and then only ten percent is checked for defects and then thrown back into storage for another 5 yrs. (if nothing is wrong). So now what can you do as a civilian to store your ammo?
Your number one enemy is moisture, as long as you have a waterproof container you are fine. I use empty 20mm ammunition containers that you can get from any surplus store although PVC pipe will do. Try and keep the cartridges in the original packing and try and keep away from metal to metal contact.
To ensure that the ammo has no moisture I throw in a couple of dehumidifier packages. This is strictly optional as we don’t even do that in the military. Whether it’s military ammo you got at a gun show or 22 shells from K-mart it’s all the same. Before you store it make sure its clean, dry( and wiped off if you touched it) and that’s it! Wow, almost too simple!
You don’t need to vacuum seal it, and you don’t need to store it at any particular temperature just keep it dry and out of the elements and leave it alone. I have been working with munitions for over 11 years, and this how the Army have trained me. I hope this sheds some understanding on storage.