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Thread: Ammo stored in severe weather extremes

  1. #1

    Ammo stored in severe weather extremes

    I keep a small sealed ammo box in the trunk of my car with a backup box or two of my usual calibers in case I'm at the range and decide to shoot more than I intended when I left the house. Most is range ammo but I also keep a couple magazines loaded with HST JHPs, you know, just in case.

    Summer/winter temps in Kansas can vary by 100 or more.

    Something tells me this probably isn't a great idea but I'd like input that's more than just speculation.

    I'd give my right arm to be ambidextrous.

  2. #2
    Hillbilly Elitist Malamute's Avatar
    Join Date
    Oct 2013
    Northern Rockies
    Im interested to know if theres any definitive info about cold in particular. We know heat slowly degrades primers and powder, but it seems consistent within the lot or batch. Someone years ago stored some 22 ammo in their attic for some number of years (10?), they had chrono info on it when fresh, then checked it after it being there a long time. It was all a bit slower, but had the same general spread of velocity deviation.

    Ive seen comments speculating about cold causing condensation in ammo, but cartridges are sealed airtight, I think whatever moisture could condense would already have to be present in the cartridge. So, other than slower velocity when actually still cold, is there any negative effect on ammo of cold?

    Ive left ammo (mainly reloads other than 22s) in vehicles all year, in some cases for many years and never had any failures to fire nor weird inconsistent sounding reports when fired. Some I still had 20-some years later and shot with no problems. It was subjected to cold more than heat.

    I do recall someone writing they left lead bullet reloads on the dash of their vehicle in the summer and had problems, but the bullets were oriented upwards, meaning the bullet lube melted and ran down into the powder, which was the diagnosis when broken down.
    Pro Biscuit

  3. #3
    Join Date
    Jul 2019
    WV USA
    Well I was a deputy sheriff and firearms instructor for almost 30 years. I learned cops of any flavor hoard ammo and keep it in their cars, forever.

    Here in WV the outside temperature swings from the teens in the winter to high 90s in the summer. Below zero and above 100 are not unheard of. The only ammo that I ever saw that seemed damaged (other than corrosion) was plastic shotgun shells that had gone fat probably due to riding around in a tube magazine in a hot cruiser.

    One Captain who was also a firearms instructor called me about 8 years after he retired Rick, Ive got some .38 reloads from when we taught with revolvers. Do you want it? He then met me with a duty bag so full of funky .38Spl 158gr wadcutters from the mid 80s that he could barely lift it. I took them to the range and if anyone showed up with a snubby for off duty qualification we gave them free ammo. I dont remember any problems with that stuff which had obviously spent a decade or two in his trunk.

  4. #4
    While I don't have a definitive answer based on science I have a few things I do to help mitigate problems. Keep in mind I live in SE Texas so I don't know much about cold (until a few days ago).

    If at all possible get nickle plated brass. I have found these to resist a lot more than plain old brass. Keep your stuff out of the direct sunlight if possible. In the trunk is best if that's an option. It will be substantially cooler even on the hottest of days there. If you put mags in the car and leave it for long periods of time it's a good idea to rotate the ammo from time to time (like once a year) and to actually function test the mag itself just as much as you do with the ammo. Extreme hot and cold (depending on the brand of the mag in question) can cause issues. Again keeping something in the trunk of your car is different than leaving it in your door panel.

    Another thing is stuff like humidity is probably one of the biggest things (at least for me). If you live really close to the ocean you might have other issues. Keeping ammo stored in sealed bag helps tremendously. Before I would use those food sealer bags and put however much ammo in those and then suck all the air out and seal it. That works pretty good for actual storage but even putting it in an ammo can will help resist the elements a great deal. You might not think of it as 'elements' because it's in your car but if you live near the ocean (IE salt water) or in places prone to really high humidity it can become an issue.

    Before I had a console vault in my previous vehicle and that thing was worth it's weight in gold. You can store ammo inside of that along with all of your valuables or whatever else you can fit in there.

    It really just depends on the type of ammo and how much of it you are keeping in your car and where in the car specifically we are talking about.

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