A common question among new handloaders is, “How long will my primers last?” The answer is that there are a lot of variables affecting that, and no definitive answer. But basically the answer would be, “If you do your part, pretty darn long. Decades, certainly. If you don’t do your part, considerably less.”
Ideally you want to store your primers in a reasonably cool environment. Now, when I say “reasonably cool,” that doesn’t mean a moderately warm environment will cause primers to degrade. Actually, dry storage in temps up to 100 degrees Fahrenheit should not appreciably degrade primer longevity or performance.
You will note I said “dry storage.” Because what WILL degrade primer longevity and performance are (1) humidity, (2) wide variations in storage temperature. I know, this could be bad news for people living in places like the American Southeast where it’s blazing hot in summer, and humid pretty much all the time, but it is what it is. We can work around that.
To start with, avoid like the plague storing your primers in unheated and uncooled outbuildings with no climate control. Such buildings suffer extreme temperature variations throughout the year, and, depending on weather, even during the same day. Yes, yes, I know, you love having your reloading setup out in that spare room in your garage, but temperature changes will cause condensation to form on steel reloading tools, including your reloading machine, and they will rust. More to the point for the topic under discussion, condensation will dampen priming compound, severely degrading its service life and performance. Bring those primers inside the house, into a more climate-controlled environment.
If you live in a very humid environment, invest in a small dehumidifier and install it in the area where you store your reloading components including primers.
It goes without saying, I hope, that we should leave primers in the original packaging, to protect them from contaminants, and impact, as much as possible, and decant them only right before use. Primer packaging is carefully designed to protect primers from contaminants and impact. I would like to think that everyone is the world is smart enough they would never simply throw a whole bunch of primers into a can or jar or other container for storage, and let them bang around off each before use, but I’ll warn you against that here, anyway.
With a little knowledge and common sense, keeping primers that will function perfectly after years or even decades of storage is easily accomplished.”
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