Ammo Shelf Life & Storage
Most manufacturers advise a shelf life of ten years for ammo if it's not subjected to high heat or moisture. Under ideal conditions ammo may last for multiple decades. If carried regularly in a concealed gun, plan on proactively replacing it every 4 months. Rotate it out and shoot it for practice at the range.
For home storage of ammo it is good practice to utilize an airtight container and to avoid storage in non-climate controlled environments like garages and attics. It is fine to keep ammo in its original packaging when placing it into sealed storage. Try to set up enough organization that you always shoot your oldest ammo inventory first. Ammo cans are available in a wide range of costs. In fact you can use any type of airtight container, even those marketed toward food storage applications.
Some people place desiccants (silica gel packs) in their ammo storage containers to scavenge moisture. And some people choose to refresh with new desiccant according to a fixed schedule. Desiccants are not needed unless you are trying to compensate for a poor storage environment or trying to keep ammo beyond 10 years. Note that the U.S. military does not bother with putting desiccants in their ammo cans.
It is acceptable to store ammo loaded in magazines. Some people worry that compressing the magazine spring for an extended period of time will wear out the spring. It does slightly, but the effect is negligible even over durations of decades. During the life of a spring, most of the cumulative degradation actually comes from exercising the spring. The actions of repeatedly compressing and relaxing the spring will lead to metal fatigue and a gradual loss of force.
If only compressed, the mode of failure is ‘creep.’ At room temperature spring creep is a slow process. For example, a stainless steel spring compressed as far as possible for 390 days at ambient temperature will lose less than 0.2% of its design force (Creep and Stress Relaxation in Springs, Sandia National Labs 2019). After 30 years, the fully compressed spring will have lost 5% of its original force.
All springs will eventually wear out after many years of shooting, and they are relatively easy to switch out with replacement springs. If you are nervous about future bans on high-capacity magazines that could limit part availability, stash yourself an inventory of extra magazine springs.
There is no problem if ammo gets wet in rain or snow for short term exposure as you are out and about for the day. It is not designed for complete submersion. Over time water can seep at the interface between primer and casing and between the bullet and casing. Though ammo may function flawlessly even after a day of submersion, it’s a literal crap shoot. Water might enter the cartridge and degrade the propellant even after a minute of full immersion. This puts the user at risk of squib rounds that don’t have enough energy to clear the barrel. For this reason, SAAMI (Sporting Arms & Ammunition Manufacturing Institute) recommends that all ammo that has been immersed in water should be properly disposed (SAAMI bulletin 9/8/16). You can contact your local law enforcement agency for ammo disposal options in your area.
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