Shelf Life on Large Pistol Primers left out on loading bench


Dec 9, 2021
I haven't loaded any 45 Colt ammo since last summer after making several hundred rounds. It's time to make more rounds and while I put the powder away, I realized that I had left about 30 large pistol primers sitting in my Lee Safety Prime Primer Feeder.

I'm just wondering whether those primers which were left exposed in my garage's hot-cold-sometimes humid conditions would be OK to use now. I would hate to make up a batch of new rounds only to have them fail to fire. Thoughts please.
They’ll be fine, takes a LOT longer than that in worse conditions to start having problems.

The primer material is sealed (At least on all the primers I’m aware of), and while heat is bad for them, as well as powder, primers are pretty dang tough and last indefinitely.
I have primed cases that I processed in the mid-2000’s and keep stored in a Folgers coffee container. I loaded some of those cases last month.

Every one has fired just fine.

Yours will fire just fine, too. :thumbup:

Stay safe.
I once bought a 1,000 box of Federal #100 small pistol primers from a shooting buddy.
He had to leave for a Dr’s appointment so he set them on a flower planter on his front porch. Along came a thunderstorm that drenched them!

I took them home and opened all the trays after draining off the water. I left them on the deep freezer in a warm storage room for about a week to dry out.
Every one popped normal!
I recently gave someone 75 30-30 cases I had primed in ‘91 that had been sitting in a coffee can without a lid on a carport since then. Temps run -10 to ~105 here and they all fired. Even gave him the AA2460 I was using back then to load them with, the rest of the 170 grain bullets I had, and loaned him the dies.

Primers are very stable long term and hard to kill.
Here’s a little primer test I did a while back. Most of the experienced guys here knew exactly how the test would turn out.

I had some shot shell primers left over from my skeet competition days. I finally used them up after 20 years and they all worked.

But, they were stored in their original containers and in better atmospheric conditions.

I recommend that you return primers and powder to their original containers if they are not used during a loading session.

With primers, I don’t unpack any more primes that I might use. I might have a few primers that need to be repacked in their original packaging but I rarely or never have a large number to repack.

I’ve always stored primers and powders where the temp and humidity is somewhat controlled. In one house, I stored primers and powder in a utility room. Every house I lived in since, a reloading area is part of the purchase decision.

Primers are pretty robust but best not press the envelope on storage conditions.
You want resilient, I ran about a dozen primed 38 special cases through my Ultrasonic cleaner with my dirty .357 mag brass by mistake one time in my solution of citric acid and dawn detergent.
They were in there for 8 minutes.
When I discovered they were in there, I set them up on a shelf and left them dry out for about 3 months, I then loaded and fired them for an experiment.
They all fired as if they were fresh primers.
They are very hard to kill.
I pick up a lot of brass and occasionally live rounds (competitions do that) and have some that make it through a 3 hour wet tumble with pins. After drying and pulling them apart, depriming and repriming they still work.

Is pulling apart reloads considered deloading?
This question always seems to come up. I keep LRP in my basement since 1991, loaded them up and worked fine.
I left a Remington 209 muzzle loader primer in the bed of my truck for several months, completely submerged in water for weeks, let it air dry a week or so and it went off!