Home Forums Hunting & Shooting Handguns The truck gun and hot days

My older daughter texted me the other day from work. It was a 90 degree, very sunny day. She wanted to know if her CCW was OK in the heat of her closed up vehicle. Having kept a loaded handgun in my truck for the last 30-some years without issue, I assured her there wasn't a worry.

But what IS the bottom line effect ?? As temperatures go up, so do pressures. At what temperature do modern powders become less stable or unstable ?? How MUCH increase in chamber pressure is there between, say, the 90 degree outside temp and whatever temperature it gets to inside a closed vehicle ?? She carries a S&W 642 with +P loads. Would the extreme temp put her pressures over "+P" ??

These things I do not know.

Glocks will melt.











So I've been told.

Mine hasn't, yet!

She also carries a G43.

I wasn't worried about that one.

Glocks have been temp insensitive since Gen 3...

Also, Glocks are not dog proof. My nephews wife, when working as a LEO, had her service Glock destroyed by their dog while they were sleeping. The barrel and slide survived the assault...but the rest of the Glock was in pieces.

Now that is just plain funny, Even the dog knows Glocks are toys.

My little guy is 70# of pisser. I’d better be careful. That said, I wouldn’t leave in direct sun.

My 19 is older than that.
Has sat in a vehicle, all seasons off and on since new.
In my wife's minivan right now.

OK......... So once we have all the Glocklove outta our systems..........

I guess what I was really asking about was the instability of ammo at extreme temps.

Think about ammo stockpiles the US military keeps in the Middle East. I doubt they are air conditioned.

Probably wouldn't matter.
Probably be a good idea to change it out.
Weekly, monthly? Who would know for sure?

This is an excellent idea, you can't be to care full I have a ammo disposal service and will handle it from here. Send me a pm and I'll provide an address for you to ship to.MB

I live in Texas where it gets pretty darn hot during the summer. I change out the ammo in the truck guns once a year just for GP. I shoot that ammo for practice and sometimes through a chrony just to see and it's always within spec. I figure it's cheap insurance to change it out once a year.

Edited to add that I have shot ammo that was in the truck for 4-5 years through a chrony and it was within velocity specs with no signs of pressure.

Rapid changes in temperature over a prolonged period of time can have an effect on ammo. The biggest effect are typically on carry guns in cold climates, where they go from very cold out door temperatures to warm in door temperatures on a regular basis. You could see a similar effect in hot climates with regular movements between hot and air conditioned environments.

Typically it takes years of accumulated affect to have any real impact. If you change your ammo out every year, or even every couple of years, you will never see a measurable effect.

If this is a concern you’re either retarded or don’t shoot often enough.

Or both.

few years ago i was breaking in the barrel on a match grade ar15, i had made the mistake of leaving ammo in the sun on the tailgate of the fj40. it wa about 110 in the shade. it started popping primers. i figured it was a combination of a tight chamber, and the heat raising the pressure in the ammo, which was not overloaded, but loaded to military specs. said later if i did it again when that hot, ammo would be kept out of direct sunlight in a cool box.
i also had a can of mace go off in the consol of my truck one time, had been left in there way too long in the heat.
and there have been a few advisory''s locally about hand sanitizers left in the car with high alcoholic content self combusting.

Most likely the latter. But your valuable input is appreciated. 👍

I would worry more about condensation rusting one than the ammo changing much. Back in the 70's I modified the driver's side shoulder seat belt reel covering to conceal a stainless J-frame M60. It was a great handgun hiding place, but once I engaged my brain, I realized that I might need the seat belt more on a daily basis than a stainless .38 Special. I don't leave a gun in a vehicle any longer.

This.


Okie John

I would be more concerned about hot handloads than any factory load