Ammo in a Fire: At What Temperature Will It "Cook Off"?


May 20, 2007, 09:37 AM
At what temperature would factory ammo (centerfire and rimfire) "cook off" without the primer being struck, just from the ambient temperature of a fire?

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Ohio Rifleman
May 20, 2007, 11:22 AM
Not sure, but it'd have to be pretty darn high. But, despite what you see in the movies, ammo "cooking off" isn't terribly dangerous. It's extremely hard for a bullet to reach lethal velocity when the expanding gases aren't contained inside of a gun. When ammo just "goes off" a lot of that energy just goes everywhere, and only a little bit goes to push the bullet forward.

May 20, 2007, 11:27 AM
You mean the lone ranger lied to me!

4v50 Gary
May 20, 2007, 11:33 AM
The Lone Ranger was ignorant of tests conducted by the NRA.

Odd Job
May 20, 2007, 11:48 AM
In his book "Gunshot Wounds" Vincent Di Maio describes various experiments where ammunition was heated in ovens. He says that .22 long rifle cartridges detonate at an average of 275F, .38 Special at 290F and 12 gauge shotgun shells at 387F. The interesting thing about these furnace experiments was that in all instances the cartridge cases ruptured, but the primers did not detonate. In fact the primers were removed from some of the ruptured cases, reloaded into other brass and fired.

When cartridges are placed in a fire he confirms that the most dangerous component of a cartridge is the brass, or fragments thereof that may cause eye injury or penetrate skin, but certainly there is no evidence that a cartridge that is not in a firearm can cause a mortal wound, either by action of the bullet or the brass/primer fragments. It is important to remember however that a chambered cartridge that detonates in a fire is just as dangerous as a cartridge that is fired under normal circumstances in a firearm.

To get a better understanding of the behaviour of free-standing ammunition in a fire, he conducted experiments with a propane torch. A total of 202 cartridges (handgun, centerfire rifle and shotgun cartridges) were used. If the heat was applied directly to the base of a shotgun shell the primer would detonate, the powder would ignite and the shell would rupture. Any pellets that emerged were traveling too slowly to be recorded on a chronograph.

In rifle and handgun cartridges where the flame was applied to the base of the cartridge the primers always detonated but the powder only ignited in half the cases and in those instances the cases did not rupture but the gas was instead vented through the primer hole.

When he heated these same handgun and rifle cartridges at the front, the powder would burn and the cases would usually rupture but with few exceptions the primers did not detonate. The velocity of expelled projectiles ranged from 58 ft/s to 123 ft/s. The only exception was the .270 cartridge where the bullet velocity was 230 ft/s. Primer velocities ranged from 180 ft/s to 830 ft/s.

As a side note he says that a revolver in a fire is especially dangerous because all the cartridges can cook off and be discharged such that there is a danger from projectiles. Only the bullet that came out of the barrel will have rifling marks and the ones that came from non-aligned chambers will have shear marks on them. Obviously if there is a question about the firing of a weapon and whether it was cooked off or fired intentionally they will look for a firing-pin impression on the primer of the suspect cartridge case.


Sciuchetti G.D. Ammunition and fire. American Rifleman 144(3): 36-38, 59-60, March 1996.

Cooking-Off Cartridges. NRA Illustrated Reloading Handbook. Washington, D.C.: The National Rifle Association of America.

And of course Vincent Di Maio's excellent book "Gunshot Wounds - practical aspects of firearms, ballistics and forensic technics". My copy is the second edition, published by CRC Press, ISBN 0-8493-8163-0
This information can be found on pages 268-270.

May 20, 2007, 07:29 PM
Take 1 30-06 round and place it primer
down in a cast iron frying pan.Turn the
burner up to high,wait about 10 minutes
for the bang.

Don't ask how i know this,i just do.:D

May 20, 2007, 07:33 PM
don't you watch tv and listen to the Brady campaign? Heat isn't needed. Guns and ammunition go off by themselves regardless of temperature! :rolleyes:

with that said, my guess is whatever temperature either the primer burns at or the powder burns at, whichever is lower..... although, I suppose if that's high enough, the lead might start to melt, and you'd just get lead splatter....

if you want to conduct an experiment, take a primer (just the primer) and heat it up and find out what temp it goes off at, then do the same with a little tiny pinch of powder (and I mean tiny!). Whichever goes off at a lower temperature is the concern.... and whatever temperature that is... is your winner.

May 20, 2007, 07:50 PM
I'm an electrician that does a lot of fire repair work. Part of my job requires me to install temp lights and power on freshly put out fires. Like we are the next ones in after the firemen. I've seen cooked off rounds, and I've seen uncooked rounds. The best thing you can do for anything of value (including ammo) is to keep it low to the ground. I've seen hershey's kissses on a coffee table that were fine, and 18" up the paint on the wall was blistered. Metal elctrical boxes also hold in heat, and damage wire more so than plastic boxes. Metal ammo cans may do the same thing. Might not though, as I have not seen any ammo cans that were low to the ground to confirm this theory. Believe it or not, but even wood boxes help. I've seen charred wood boxes, were the stuff inside was fine. Bottom line is keep your stuff low, and water proof and you should be OK. Next best thing is to keep it away from the kitchen, bedrooms, and laundry/furnace rooms. Those usually burn the most often.

The Real Wyatt
May 20, 2007, 08:15 PM
I recall conducting an experiment along about 1951. I used an empty 12 ga. shotshell (it was empty 'cause the powder had been put to good use elsewhere, but that's a another story) with the paper shell cut off at the brass so all there was was the primed brass part of the hull.

I put brass, primer down, in one of mom's aluminum cooking pans and placed it on an electric burner turned on HI. Wait a few minutes ... BANG! The shotshell brass hit the ceiling with not much force at all, but the primer was driven downward with enough force to completely pierce the bottom of the pan.

Mom wondered what ever became of her pan, but never did find out where it got to.

May 20, 2007, 10:52 PM
Thanks for the replies, especially Odd Job. I posted this question because I am a volunteer fireman and there are many times that a call for service comes in while I'm armed. I have been reluctant to carry when the call is for a fire for just the reasons in Odd Job's post, but also don't want to unecessarily delay my response while safeguarding the weapon. I already knew that ammo not loaded in a firearm is relatively harmless, but was wondering what the risk was with ammo in a handgun. Structural fire temperatures can easily exceed those Odd Job cited as the cook-off points for common ammo, so my instinct is confirmed. I'll just continue to safeguard the weapon(s) as quickly as possible before responding. Thanks.

May 21, 2007, 12:11 AM
your best bet is to keep it somewhere where it will take a long time for the fire to get to.

ive seen a few houses on the news that burned to the ground because once the fire dept heard rounds cooking off they refused to even go near the house until the popping stopped and the house was lost.

May 21, 2007, 08:40 AM
I store my ammo in an old 1/8" steel gunsafe (locker) and feel confident that no one will be at risk in the event of a fire.

May 21, 2007, 11:02 AM
If your gun gets hot enough to cook off the round while concealed on your body while fighting a fire, I think you are going to be worrying about the fire having burned through your protective equipment more.

May 22, 2007, 06:35 AM
OddJob thank you for a most excellent and thorough reply, I greatly appreciate the data source info.

Again thank you


Double Naught Spy
May 22, 2007, 08:01 AM
I have demo'd this several times at my place for people, but only as an example of what happens, not by temperatures. We place a few rounds out on a bare spot and use a liquid fuel source. The source is ignited and we move back about 20 yards and watch (eye and ear protection). Being at the bottom of the flames, it can take a while for the rounds to cook off, up to a couple of minutes. We count the pops to determine when all are done and wait for the fire to die down.

On inspection, we can usually find about 20% of the slugs, either almost in original position or within 2-3 feet. The slugs don't usually move too far. The cases, however, can be see flying out of the fire out to about 30 feet (9mm ammo).

M2 Carbine
May 22, 2007, 12:30 PM
In 95 my shop burned down. The best estimate is I had 23,000 loaded rounds along with a lot of gun related stuff.

It's mostly true that ammo in a fire will just pop and maybe just throw a little brass a short distance.

BUT from that fire I'm witness to the fact that ammo can also "fire" with enough force to go through steel 50 cal ammo boxes and continue through such things as walls and cans.
There were bullet holes through the shop's paneled and insulated tin walls.

The ammo does strange things.
All the ammo "went off" in one 50 cal can and none escaped the can, while other cans has mutable holes through the can and dents where the base of the case hit the can with a lot of force.

A fist size hole was blown out the bottom of a can that was about 20 foot from the fire.
The can contained 9mm in plastic boxes. About 35 rounds, in one box, apparently decided to "pop" all at once. It's interesting that the ammo closest to the fire didn't blow.
The gun is a Ruger 22 that I had for years.:(
There were seven guns in the fire but none were loaded.

These are smokeless powder cans, WD40 cans and a couple Black Powder cans.
The WD40 and Black Powder cans blew up.
Note the bullet holes in the couple lower center cans. In order to hit those cans the bullets would have already had to go through a steel 30 or 50 cal ammo can.

May 22, 2007, 01:03 PM
Many years ago when I was younger and invincible :rolleyes: . My cousin and I were hunting in the mountains. At night, around the camp fire we were talking about all sorts of things. One of us wondered what a cartridge would do if thrown in the fire. Well! We took a .45 ACP round and threw it in and hid behind trees. A small "pop" was heard and we thought "That's it?" Well, that only peeked our curiosity. We tried the .45 ACP again with the same results. Next we tossed in a couple of .22 LR. Now, this time there was a very distinguishing and loud "POP." WOW! Of course we tried it again with the .22's. Again "POP," almost a "bang." We had a .45 LC so of course we tried that as well. Very disappointing! A small "pop" was heard each time we tried that. He had some of the .45 LC loaded with black powder so we tried them. There was a definite "BANG." The only other ammo we had was 30.06 so we tried our experiment with a couple of these as well. Again, hardly anything. Our very un-scientific analysis was that the .22 LR was the most dangerous of the modern powder loaded ammo. The Black Powder cartridges, of course being loaded with a low grade explosive, were quite impressive as well. (Actually dispersing the embers and wood from the fire setting off a rapid scramble on our part to ensure we did not burn down the forest :eek: )
Now, with experiments such as this it is a wonder we are still alive. We didn't wear helmets when we rode our bikes either :what:

May 22, 2007, 01:34 PM
WOW! those are some interesting pictures.

May 23, 2007, 07:52 PM
I did not see the NRA article on these tests, but as far as I can tell, nobody has mentioned if there is any difference between brass-cased ammunition and steel-cased of the same type.

Can anyone enlighten me?

Hatcher did the same experiments quite a wHile ago using an electric welder to set off the primers. He did not record temperatures, merely the effects on the surrounding cardboard box.

The effects were minimal on the cardboard boxes which covered the rounds, so I wonder why the rounds in the ammo boxes seemed to develop so much energy.

He also placed cans of powder on a small fire and the results were unimpressive except with the black powder.

That was an interesting remark about the metal junction boxes causing more damage to the wires than the plastic ones. Very interesting!

Great job, Odd Job!

May 23, 2007, 10:43 PM
I went through a house fire in the 90's. I had considerable ammunition stored in my garage. A pallet with 20 flats of shotgun shells and approximately 10,000 mixed center fire handgun and rifle cartridges. I also had 4-5 pounds of smokeless powder on hand. 100% of my ammunition either cooked off or was destroyed by the fire, but "none of it exploded or launched a projectile with significant velocity ". All of my ammunition was stored in factory pasteboard boxes and in wooden crates or lockers. Modern "smokeless powders" are propellants and not explosives. If smokeless powder is not confined as in the chamber of a gun or in another type of strong container (i.e.: the military ammo cans), it burns hot but does not generate sufficent pressure to explode. The factory containers are designed to prevent explosions. Today I store my ammunition in modified Homak gun lockers. I have added shelves and drilled vent holes to relieve pressure in case of fire. For those of you that still believe in military ammo cans, think about it. The military uses these cans to move ammunition through water , mud, snow, sand, rain and delivers it by “kick-out” re-supply from helicopters, boats, trucks, and planes. The military ammo can is great for it’s military purpose, but as civilians we don’t need to give up the safety of the factory packaging for the ability to lug ammo through the muck and mire. Sorry about the long rant, but even 10 years later the house fire is a low spot in life.

PS One added note, black powder is an explosive and will go “ka-boom” in a fire. I store mine in a shed away form the house. And yes, I do lock it up in a military ammo can. A 20MM can with padlocks. It is going to go blow regardless, so I make sure kids can’t get in to it.

May 23, 2007, 11:48 PM
According to Peter G. Kokalis the ignition temps for small arms propellants range from 180 to 200 degrees Celsius.
This is from the April 10 2006 issue of Shotgun news that I happened to be reading this morning.

M2 Carbine
May 24, 2007, 12:48 AM
WOW! those are some interesting pictures.

Here's a couple more.

This is the 50 cal box that didn't have a single hole in it. As I recall it contained steel case Chi Com AK ammo.
Note the damage to and the holes blown through the other steel ammo boxes.

These two cans contained 30 Cal Carbine.
You can see there was some metal flying around with quite a bit of force.

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