Virginia Gun Owners Forum - VGOF

Admit it, you've picked up a firearm that's been out in the sun for a while and gone "WOW....THATS HOT!" But have you ever wondered just HOW hot?

Wonder no longer

Virginia, Mid July
Ambient Temperature 91 degrees with a very light breeze, clear skies and sunny.

CZ-75 Compact
FN FNP-9

Both test subjects started at near ambient temperature and were placed near each other and left in direct sunlight for approximately 30 minutes.

CZ-75 Compact (aimed at frame just in front of safety lever)


The black polymer coated and all steel slide and frame of the CZ soaked up a LOT of heat. The gun was simply too hot to pick up or touch except for the rubber grips which were just "very warm". The gun also took quite a while to cool back down and was still noticeably warm when I re-holstered it later.


FN FNP-9 (Aimed at slide just behind extractor)

The matte stainless slide on the FNP-9 certainly didn't absorb as much heat as the CZ did but it seemed like it actually took even longer to cool back down to ambient (sadly I didn't think to time it). Interestingly enough the polymer frame was "only" 107 degrees.

Just for comparison, hot water at 140 degrees can scald in as little as 10 seconds and it is recommended that a hot water heater be set no higher than 125 degrees.

at what point do you think a gun could get too hot that it would fire.... I heard a story about a hot gun firing at a range once...not sure I believe that story or not...is that possible?

I'm not saying it's impossible but I really doubt that the sun alone could heat up a gun enough to discharge a round. I'm pretty sure I read that most gunpowder has a "cook off" point of somewhere around 450 degrees Fahrenheit though now you've got me wondering so I'll have to try and find that information again.

Yes a cook off is possible if you had a weapon that you fired past a reasonable sustained rate of fire for a period of time. but it would be several hundred degrees.

if I remember the story right it was a rifle (deer gun) maybe .270 or 30'6...I've never heard of that w/ a rifle before...now a shotty I might believe that, hell I've seen a shotgun fire from being dropped before so nothing would surprise me w/ a shotgun

on mythbusters, they tested this theory. they used a revolver and put it in an oven and sure enough, the bullet went off due to high heat. they even tested ammo by itself and once it was hot enough it would go off. the funny part about that, was that the bullet itself didnt move much, but the empty casing flew everywhere because it was lighter. i assume most ovens dont go over... 500 degrees? so say between 4 and 500

Snazuolu wrote:on mythbusters, they tested this theory. they used a revolver and put it in an oven and sure enough, the bullet went off due to high heat. they even tested ammo by itself and once it was hot enough it would go off. the funny part about that, was that the bullet itself didnt move much, but the empty casing flew everywhere because it was lighter. i assume most ovens dont go over... 500 degrees? so say between 4 and 500

350-450F is common cooking temps. All the ovens I've seen could do 500F and a few did 550F IIRC.

Smokeless powder burns, it does not explode. It provides an explosive like event only when confined in a small space. It is still burning, just burning very fast. Smokeless powder storage recommendations are for 1" thick oak cabinets/barrels with brass fittings (no steel and such to reduce static concerns). White oak is preferred IIRC. 1" of oak provides approx. 1hr of burn time before it reaches the powder. The storage cabinets are suppose to have vents or loosely constructed so that when the powder does ignite, it is just burns. No explosion.

Without a barrel, there is nothing to direct the pressure and the bullet is many times the mass of the casing, so the casing is propelled much further than the bullet.

At Quantico (FREE 3 GUN MATCH!), we were to shoot 4 rifles left in the sun @ 300 yards. One was an FN-FAL with iron sights. That bastard was so hot, I wanted to drop it, but I refused to embarrass my civilian ass in front of Uncle Sam's Misguided Children. I hit all 4 targets using all 10 of the available rounds in the gun, and went on to place 2nd in that phase out of 140 shooters. Black rifles get hot!

The brass I later picked up that was left baking in the sun was clearly hotter than that immediately ejected from the USMC provided M4's.

The sun is more powerful than the urge to pee after a 12 pack!

Had some first timers out yesterday. The guns getting hot from sun exposure was an issue, aside from the general heat. I had one of my asbestos mitts but forgot about it until cleanup time.

Anyone that has ever shot an M-60 will tell you that cook offs are not a myth...they can and do happen even to the most mollycoddled of guns...

This is exactly why I like covered Ranges/Benches.

Wonder what readings you would have got with our recent over 100 degree Temps?

"If" I leave my weapon on the Bench,it gets covered with a towel.
Plus I can wipe my sweat.

Usually I holster it.

zephyp wrote:Anyone that has ever shot an M-60 will tell you that cook offs are not a myth...they can and do happen even to the most mollycoddled of guns...

I still haven't figured out how an open-bolt gun can cook off.

Diomed wrote:

zephyp wrote:Anyone that has ever shot an M-60 will tell you that cook offs are not a myth...they can and do happen even to the most mollycoddled of guns...

I still haven't figured out how an open-bolt gun can cook off.

Poor design. The M60 is a POS and have been known to cook off. You're right though, any gun that fires from the open bolt positions, like most MGs, shouldn't be able to cook off.

A little while after the initial thread someone in another forum asked me about guns in the car so since I had my Jeep safely in the back yard for some maintenance I put the gun on the dash and left it there for a while...171 degrees!

gunderwood wrote:

Diomed wrote:

zephyp wrote:Anyone that has ever shot an M-60 will tell you that cook offs are not a myth...they can and do happen even to the most mollycoddled of guns...

I still haven't figured out how an open-bolt gun can cook off.

Poor design. The M60 is a POS and have been known to cook off. You're right though, any gun that fires from the open bolt positions, like most MGs, shouldn't be able to cook off.

The M-60 is kinda like a whiny woman. Takes a lot of effort to get anything out of it and constant coddling, stroking, loving. And, to really get the most out of it you need a helper...

zephyp wrote:

gunderwood wrote:

Diomed wrote:I still haven't figured out how an open-bolt gun can cook off.

Poor design. The M60 is a POS and have been known to cook off. You're right though, any gun that fires from the open bolt positions, like most MGs, shouldn't be able to cook off.

The M-60 is kinda like a whiny woman. Takes a lot of effort to get anything out of it and constant coddling, stroking, loving. And, to really get the most out of it you need a helper...

I don't believe that a gun would ever get hot enough to cook off ammunition just from exposure to sunlight or Soldiers and Marines would be having accidental/ negligent discharges all the time in Iraq. I do believe they can get hot enough to be too uncomfortable to handle. Twenty couple years ago in Egypt, we just sucked it up, now if you look Soldiers and Marines are wearing gloves to make it easier.

Any firearm that has fired a large quantity of ammuntion in a short period of time is susceptible to cooking off rounds. Machine guns, due to a high volume of fire, are the most likely candidate. The main reason that most machine guns and most older non-selective sub-machine guns fired from the open bolt position was to prevent cook-offs. Even the Browning M2 .50 caliber, which fires from the closed bolt position, will. It just takes longer to heat up than most, mainly because of it's slower rate of fire and the fact that it's barrel alone weighs 26 pounds creating a giant heat sink that takes a while to heat up. I would not encourage anybody to test this with their firearm because I don't believe in abusing weapons, but if you put 200 rounds through your AR or AK in as fast a period as you could (it could easily be done in less than two minutes and less than one by some people) and then left a round in the chamber, I believe it would cook one off too. That is why the Military trains Soldiers and Marines to understand cyclic rate, rapid fire rate and the sustained rate and how quick to change the barrels on machine guns when firing those rates.

I won't argue that the M60 wasn't a tempermental machine gun, it required a good crew and good armorer to take care of it. If you didn't have either, that gun was going to cause a lot of headaches. The sad part is most of the time $20 worth of parts would make the gun run good for 6 month to a year before they needed to be replaced again. Another reason that the guns were a headache was the operator maintenance that was performed on them was sometimes harmeful. All soldiers are taught to keep their weapons clean and have them spotless when they turn them in. The problem with the M60 was a part called the "gas piston", the manual said don't touch it as long as it was moving freely, the reality is the Sergeants made gunners pull them out and polish them until they shined, usually with a 3M green scrubby pad, which really acts like sandpaper and slowly over time makes the piston smaller than the bore it slides in. So it takes a few rounds of single shot fire and "Pull, Observe, Push" to get the carbon built up and able to seal the piston so it moves far enough to cycle the gun. As the armorer, another problem that I had was, that Soldiers were inaccurately identifying the problem that the gun had. They almost always called it a "double feed"( trying to push 2 round into the chamber), when the real problem was a "failure to eject" (pulling the fired case out of the chamber, but not throwing it out of the gun. It then grabs the next round and trys to shove it and the fired case into the chamber together.). On a hot gun, the heat that built up in the chamber would cause that round to cook off.

Most Vietnam Vets seemed to think otherwise about the guns, but they had them when they were much newer than when I worked with them, first as a machine gunner and later as an armorer in the early '80s. I took a lot of pride when the Battalion went to shoot and all of my guns stayed running the whole day at the range, when the other companys' guns went down and at the end of the day of the 10 still firing, 6 were mine. The downside to that was, the guns were at the end of their service life and I had to turn in 4 of them in one year for replacement, because the rivets holding them together were going bad and the guns were just wore out.

Ah Greg, sounds like we chewed some of the same dirt. My first experience with the 60 was back around 77. We had a sorry armorer and even sorrier weapons. Sorry to say. Training and experience were piss poor. My first assignment was a TOW company. The TOWs were ok but the .50s were in horrid shape. Every spare barrel I saw was coated with rust inside and out. And, you were lucky if you had a spare barrel much less an asbestos glove. It seemed like we had the worst of everything. Them were the good ole days though.