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Is It Safe to Store Guns and Ammo in a Hot Car?

August 29, 2013 | by
Is It Safe to Store Guns and Ammo in a Hot Car?

Is It Safe to Store Guns and Ammo in a Hot Car?

Recently, we had a heat wave in Southern Utah and there were a string of 100-degree days. Thankfully, I’m a little bit north of Las Vegas so it didn’t get to 110, but it was still extremely hot. When it gets this hot over the summer I often get several questions about storing a gun and ammunition in a car, and if it’s safe to do.

Let’s start with storing ammunition first. If you’re using quality factory ammunition then you can store it in your car all summer long and it won’t be a problem. A lot of people believe that if it gets too hot in the car the ammunition will explode and you’ll have the Fourth of July inside your vehicle.

But the fact is, it has to be over 400 degrees inside your car in order for the ammunition to “explode.” And if it gets that hot in your car you’re probably not on Earth, but in a place governed by a fellow with horns and a pitchfork.

The big problem when it comes to storing ammunition in the car is humidity.

If you live on the east coast then you know how tough the humidity is. Walking from your house to your car in the morning can leave you drenched in sweat. But as I mentioned a minute ago, if you’re using quality factory ammunition (which is sealed) you still won’t have a problem.

The problem is when people reload their own ammo and they buy inexpensive primers that aren’t sealed. This allows moisture to get in and cause the round not to function.

As far as storing a gun in your vehicle, it’s pretty much the same as storing your ammunition. You can store your gun in your vehicle in high temperatures without a problem. However, if you’re storing your gun in your vehicle long-term I would definitely lock it up. When I was a police offer I knew several people who left their guns in their vehicles and thieves broke in and stole the guns.

Like ammunition, the major problem with storing your gun in your car is humidity.

If you have a 1911, you might find a gun with a lot of rust on it after a summer of sitting in your vehicle. However, if you’re absolutely dead-set on storing your gun and ammunition in your car in the heat a simple solution is to put them in a small cooler.

I know a few folks who put them in a cooler and they tell me this solves the problem and they’ve never had an issue with humidity or a rusted gun. Personally though, the only time I leave my gun in the car in the heat is when I’m running an errand to the post office or I have to go to the courthouse or some other place where I can’t bring a gun. Otherwise, I prefer not to leave my gun in my car for extended periods of time (mostly because I don’t want to take the chance of someone stealing it) but obviously, you can do what suits your comfort level.

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  • David Crutchfield

    I’d say the biggest reason why you do not want to store your weapon/ammo in your car is because of theft! Especially if you have any indicators on your vehicle, say an NRA sticker or one of those stickers that say “Protected by Smith & Wesson”, ect. You get my point…
    This just makes your vehicle that much more of a target. Criminals are not entirely stupid. They will look for a weapon of you have any indicator that their might be one in the vehicle. Just my two cents worth on the subject.

    • Karen

      You have a very good point. I hadn’t thought about a sticker on my car could be an indicator that there is a gun in it. I was about to put a sticker on my car. I’m not now. Thanks

      • mike

        Put an obama sticker on it then no one will think you have a gun in there…

        • jamohio

          Good idea, but NO!! lol

        • Master99

          Not true, they will think you have drugs and a stolen gun in there.

  • dave

    The comment about primers made me wonder – would a drop of hot paraffin or a touch of petroleum jelly on the primers keep the humidity out? You know, like dipping stick matches to waterproof them….

    • Pastor Rick

      Do you really want to have residual wax residue (or anything else) retracting back on your firing pin/striker/hammer? Just buy quality ammo for Personal Protection and store your cheap target ammo appropriately.

    • Andy

      I cant remember the name of it but there is some liquid stuff to put on the primers and bullets to keep out moisture. I have heard of people using clear fingernail polish too.

      • 2ThinkN_Do2

        The product is: Markron custom bullet & primer sealer. It comes in a bottle that resembles a finger nail polish bottle.

  • 2ThinkN_Do2

    This topic has been on many shooting websites lately. Upon research at many sites, it is possible for the temperature in an auto in the sun to get close to 200 degrees. That type of heat would require air temperature over 100 degrees and direct sunlight. In general, your car won’t experience temps above 150 in most parts of the country even if it’s 90 to 100 outside. I’ve read ammo tests that say it takes over 300 degrees for ammo (primers) to cook-off and Mythbusters did a test some time ago in an oven scenario. Bottom line as stated here, nothing to worry about. As for sealing the primers with paraffin or petro jelly, it would probably melt off; get some Markron (brand name) available at many shooting supply stores.

  • Nathan Redbeard

    I used to store some ammunition in my non-climate controlled garage in Houston. One summer of that taught me it was a bad idea. I had a good quanity of .40 S&W target loads that winter for cheap (like 24 cents/round) that shot very well and was accurate. I ended up not shooting half of it from around march to spetember, and when I pulled it out, there were black stains on the cases and it shot horribly, my average group size went from 2″ to 6″ at 10 yards.It’s only ancedotal, but I now store all my ammo in the house, where moth and rust (and humidity) cannot destroy.

  • Richard

    This article has valid pints, however I can’t agree with some things. The temperatures inside an automobile will never each the temperature required to ignite a primer. However every ammunition manufacturer recommends that ammunition be stored in a cool dry place. I live in the southeast and cool and dry are never used in the same sentence in the summer months. If the inside of a vehicle reaches 130 degrees on a hot sunny day and remains that temp for several hours, what is it doing to the ammunition? Let’s put a different spin on it. What is the difference between ammunition being inside a hot vehicle for several hours every day, or storing you ammunition in your oven set at 130 degrees for several hours, every day? Here in the hot humid southeast I advise my students if they store a gun in their vehicle to notate the date that the gun was initially loaded, inspect the ammunition regularly and after six months cycle out the ammunition. After all if you haven’t fired that gun in 6 months you are way out of practice.

    • Blogengeezer

      Many years ago, friends and I were in a dry arroyo range commonly used by various shooters. The NM sun is brutal at noon on a hot summer day. Several guns were sitting on the hood of a dark car we used as a table. One of the .22 rimfires ‘Cooked’ off, as the heated weapon was sitting idle for an extended period. Fortunately it was pointed downrange. The experience alerted us to shelter them inside the car for the duration. No rounds were left chambered…. after that surprise.

  • jar1807

    good stuff jason.

  • the real diehl

    Military ammo is sealed with a laquer type sealant over the primers to stop moisture.
    This makes reloading military brass a little more work. That is removing the sealant
    before depriming.
    About stickers, I have never had an NRA sticker on my cars or house window for the reasons already stated. I don’t wear a lot of clothing advertising my intrest in firearms for similar reasons. If I ever have to use my CCW to defend myself or someone else, those kind of pictures would not make make you look to good to the media and anti gun freaks. Nor do I want to advertise that I might be carrying.

  • Docs150

    I used to leave my S&W 686 in the vehicle 24/7 for years…taking it out now and then for a wipe down/check- It was my truck gun/go to anytime firearm. I would rotate ammo just to make sure but anything I ran always worked.(MS weather). Now I don’t leave anything in overnight or if leaving vehicle for long unless I use the deep concealment spot under the console. There is no need since I’ll have one on me anyhow. Nothing like stainless///

  • bikerbill

    I have had a Taurus 85 locked in my car for years, through some of the hottest summers Texas can produce. I do rotate the ammo, but that’s just common sense. I keep the gun in a silicone-impregnated Gunsock and there is not a touch of rust anywhere. Theft is an issue, of course, and you will have to deal with that on your own. But heat, in and of itself, will not cause any issues with your gun’s performance if it is properly protected …

  • davidz71

    Wax lubricated bullets in ammunition such as 22LR or 38 Special round nose lead can leave wax oils around the primer area and can contaminate it. I’ve left half a brick of 22LR ammo in a hot van during a pistol match and when it came time to compete in the rimfire division, one of three rounds failed to fire. I came back home and tested the remaining rounds and all fired. I never leave that type of ammo in a hot environment.

  • 2ThinkN_Do2

    Lock It Up all the TIME if leaving it in your vehicle, For ANY length of TIME. quote from the article: “However, if you’re storing your gun in your vehicle long-term I would definitely lock it up.” Thinking like this is why a young child shot and killed his sister in WA. state. A gun left unlocked in a vehicle, by a police officer no less . . . . . while the children were in the vehicle. Never leave an unattended gun unlocked if it is not within your sight and access before anyone else.

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  • Jeffrey T

    I read someting about this and they recomment to reloaders to use finger nail polish! Clear of course and used sparingly where the primers seat. Aleviates the moisture creep tgey talk aubout

  • Jim

    Vietnam is the hottest most humid place I have ever been. I know of no incidence where ammo cooked off because of heat and ammo was stored in Tanks, out in the sun and everywhere else. We had ammo cook off, rockets too in Helicopters but they had crashed and were on fire.

    • Nattleby

      Wow. Didn’t Charlie store their ammo in mud pits and under water and all kinds of other places that you wouldn’t want to store ammo in?

  • Fanfare

    You mentioned that you leave your gun in your car when at the post office. I believe I read an article where the parking lot of a post office is federal property and even a gun left in your vehicle is illegal. Anyone know more about this?

    • Isaac

      Recently a federal court ruled that the post office cannot regulate firearms in the public parking lots. They can however still limit firearms in the employee parking lot and the building.

      • Joey Cee

        I don’t know, I’m asking a question. Are you saying you cannot carry into a post office? I recently obtained a ‘mini’ carry pistol. I asked my post office person if I could carry legally into the post office. He said he knows of no reason why I couldn’t. It wasn’t a good enough answer for me so I do not carry into the PO.

        • osiris

          As far as I know, all post office buildings, along with other federal buildings such as courtroom buildings and detention centers (“prisons”), prohibit firearms. I never take my firearm with me inside the post office because I wish to live the next 10 years of my life in a room bigger than 8x6ft. Luckily, I rarely have to go to the post office. I would strongly suggest not taking a firearm inside any post office building – state and local laws may vary but I’m pretty sure that’s a federal law when it comes to post office buildings.

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  • Bret P Hooyman

    Thanks for the info. I live in the Phoenix area, and have been concerned about leaving both weapon and ammo in the car while I’m at work. Now I feel a bit more comfortable doing so after reading this.

  • Mr Ghue

    I have heard of nitro sweating from black powder and my main question that brought me here was about leaving optics in a hot car or storage of said optics in my attic. I like to hide my rifles there when I go out of town. A thief wouldn’t look there.

  • Russell Bruneau

    I think that most people who look at this or have asked the question are people who are not allowed to carry at work. Which sucks to say the least. But atleast we are trying to be as safe as possible about the whole situation. Like today for example. It’s about 80 where I’m at which is pretty warm for April. Got on my lunch break and went to go grab something to eat and grab my pistol and feel how warm it is. Hot to the touch and pull the mag and its extremely hot too. Just worried about my handgun. And to the person about the stickers on your car I have a giant blunderbust on mine with a local gun shops name above it and a guy pissing on anti gun groups. I don’t park my car in areas where I believe it’s going to be broken into. And if I am in an area where someone might try it you can bet your ass I’d have my pistol on my person. Love in a town with 1500 people, and work in a town with 2000. Around here we aren’t really worried about car theft.

  • Mike Reaves

    Have some balls. Put a “Trump 2016” sticker on your bumper. Wear a “Make America Great Again” ballcap. If you are afraid, then the bleeding heart libs, the BLM boons, the ragheads, and the terrorist Obama have already won.

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