Firearms/ammo in hot car?

[Lightfoot4]

Sometimes I have to leave my firearm and/or ammo in the car. During the summer months, the inside of the car can get pretty hot. But how hot is too hot for ammo? I’m going to measure the temperature over the next few days to see what maximum I get, but what would be the limit for having ammo in there?

Thanks.

 

[Erich]

This comes up every summer. I've yet to hear of a round of ammo cooking off in a car, and I don't myself worry about it. Temps here only get into the low 100s, but obviously the car gets warmer than that inside. As I said, though, I've never heard of this being a problem anywhere, and I don't worry about it.

 

[BreakerDan]

Ammunition is a relatively stable thing. I have never heard of ammo cooking off in a vehicle. The temps in Iraq would be close to the temp inside a vehicle and I have not
heard of ammo problems over there.

The only issue heat poses to ammo that I know of is it can melt the glue inside of shotgun shells and dampen the powder. I try to keep the shotgun shells cool but other ammo I carry
without worry.

Just think about all the ammo that rides around in police car trunks all over the US.
A police car trunk here in TX can get very hot. Ammo has to get several hundred degrees
from what I have heard to even get close. Also, it should not affect the performance of the
ammo either. I regularly fire ammo from the 1940s- long before air conditioning was common and I have not experienced problems. People worry too much these days.

 

[Lightfoot4]

Thanks. I had the same thought exercises myself. I figured if ammo can survive in desert conditions, it should be okay in my car. “Hot” can be so relative. But I thought I’d ask anyway, to see what the experts out here thought. Thanks again.

 

[n4zov]

I've posted this before, but I will repeat it again! If the ammo has cast bullets, it is highly likely that the bullet lubricant will melt and contaminate the powder resulting is squib loads. I once ruined 500 rounds of handloaded .38 Specials by storing them in a car trunk in the middle of summer.

 

[Landpimp]

I had a cheap chinese lighter blow up last week, it was 80-ish out, black car, windows up......glad I wasnt in it.

ammo....aint blown up yet

pretty sure my guns wont melt.....even the plastic ones

 

[OKFC05]

"This comes up every summer. I've yet to hear of a round of ammo cooking off in a car"

And I'll add my usual comment: Primers start to cook off above 300 degrees F.
So if your ammo is cooking off, your car is on fire.......

 

[indiandave]

Myth Busters did a show about Ammunition once. It took about 450 deg. to set the ammunition off.

 

[danski]

A thought about ammo pressures in hot weather and this came up every year at an outdoor range where I sometimes worked.

Some handloaders have the bad habit of going above recommended powder loads because they don't see any pressure signs nor feel any excessive recoil. Trouble is,
those loads were made up in cooler weather, say February, and then carried outdoors.
Once those "overloaded" rounds got into summer, pressure shot up and we saw several rifles blow because of that.

It was always amusing to listen to the factory or handloaded shotgun rounds in February, when temps were around zero. Cute little pops rather than the usual 12-gauge blasts.

 

[Erich]

Then there's Blue Dot, which appears to have pressure spikes at low temps . . .

 

[HAWKEYE10]

I think heat and cool might weaken powder over a
period of years. I know powder will last for years at
room tempature. I think for the short term,not to
worry. Don [/U]

 

[jkc]

There's no worry about "cook off" or spontaneous ignition, even in this neck of the woods, at 1,100 feet above sea level, and ambient temps of 110 or more in the summer. However, higher ambient powder ignition temperatures equal higher load pressures/velocities when tested/zeroed at high temperatures than at low temps. The load you test and zero at high temperature won't perform equally at low temperature.

Also, elevation differences alter external ballistics, because of differing air density/drag --- sight in your rifle at the altitude at which you're operating.

 

[GatorFarmer]

Supposely some professional hunters had problems with .416 Remington mag ammo in hot weather. There were reports of sticking cases, difficult extraction, etc. The story making the rounds was that pressures had somehow increased (the cartridge was already a "hot" one) owing to the temps. Shrug. It was accepted enough to make the rounds of stories in the gun mags and for the cartridge to be discouraged for big game use by some safari outfits.

There have also been individuals who've claimed that long term storage of ammunition in hot conditions can lead to problems with the powder breaking down over time.

Is that per se Gospel truth? No, it isn't. But it's something worth keeping in mind. I had problems with WWB 9mm stored in a non climate controlled storage area that went through two winters and a summer. Certainly storage conditions can be an issue at times. Thus I wouldn't leave ammunition sitting in the trunk for years or anything of that nature if it was meant for self defense.

 

[a1racer]

Myth Busters did a show about Ammunition once. It took about 450 deg. to set the ammunition off.

i loved that show and yup it took a lot of heat top set the round off.

 

[ACP230]

I spilled a box of Remington Thunderbolt .22 ammo in the glove box of my old van.
When we gave it to my daughter I finally cleaned it out. It had been in the glove box summer and winter for about four years. That included -20 degrees in the winter and some 96-100 degree days in summer.

I cleaned it out at the range and shot it right after a box of Thunderbolt that had been stored for the same length of time in the house. The glove box ammo all fired and was as accurate as the stuff that had been treated more gently.

I wasn't too concerned about ammo in the car before that. I am less concerned now.

 

[kcoruol]

My wife won't let me store ammo in the oven, frig, or freezer. Other than she's pretty tolerant.