Collections auto-igniting?

Smokeless powder breaks down over time, that is a fact that much chemistry has been invested in over he last 100 years. The volume of the smokeless powder obviously has a great influence on how fast the chemical process goes and how much energy is given off from the process. Ammunition fires are rare now and the chemistry behind the process well understood and a program for analyzing how much stabilizer is left in the powder has been running for many years. … ab_eq.html
In the above linked article they mention the fact that old small arms ammo can be unstable when pulled apart.
But un-pulled SA ammo have not been the cause of any fires or has it?
Do we know about any normally stored collections that has been the cause of a fire?

(I think I have asked this question before, but can’t find the relevant post…)

In the German ECRA journal there once was a report about a caseless cartridge (from WW2, I am not sure) that had obviously self-ignited. But it caused no fire, the fact was only discovered some time after it had happened.

Deteriorating propellant heats up. The products from this process in turn speed up deterioration. When stored in bulk containers, there is no way for the heat to dissipate. Enough heat can build up to ignite the propellant. At military depots which store old propellants this actually happens now and then. (By the way, the same process applies to old nitrocellulose-based film. A storage bunker at the old location of Bundesarchiv was destroyed by spontaneous ignition. Thats why they use bunkers.)

In cartridge cases, the heat can easily dissipate under normal circumstances. The propellant decomposes but never gets hot enough to ignite. I am very, very sceptical that pulling the bullet should have any role in this.

Projectiles that contain incendiary loads are a totally different matter. Never trust them.

OK, you confirm what I had suspected, i.e. that the small amounts of powder in SA cartridges will not self-ignite. If pulled, the amounts stored together would rise depending on the size of the container, if for example the pulled powder were stored in a 100 liter plastic drum, the condition of the powder -near end-of-life, could very likely ignite the old powder from the exothermic heat made by the decomposition process.
That is why I destroy old powder when the amount has gotten up to a pill container full.


I seriously support your practice of minimizing the amount of outdated propellant accumulated at any time, any where, as you describe.

However, having been involved in the investigation of two incidents of propellant apparently spontaneously igniting, and as I have reviewed a small number other related accident reports. From my knowledge and experience, I would have to say that your use of the phrase, “very likely ignite” could be misleading as a minimum. Of the millions of tons of various propellants stored and allowed to remain in storage past servicable conditions, and the very few instances over history where spontaneous ignition was suspected, it seems to make it a VERY VERY unlikely scenario.


Former Chairman, Department of Defense Explosives Safety Board (DDESB)

Would there be any increased risk in larger-caliber ammunition, for example cannon rounds in the 30-40mm range? Or would these rounds still be able to safely dissipate heat from propellant decomposition?

Taber, I am only basing my assumptions on what the army logisticians tell me. The mostly german powder I remove from 7,92 cartridges is from production runs from 1944 onwards where quality went down fast. Powder that stinks of acid gets destroyed immediately. But considering that this german powder has lasted up to 68 years or more and only managed to etch itself through the case walls, I’m not too worried.

The only times I’m aware of this was some years ago when Doug Culver (who very probably will be at SLICS) reported a round which had been displayed in a window & I can’t remember his exact words but something like disintegrating, or coming apart.

George P. (of Phoenix AZ) left, I think he said it was some Japanese INC, rounds on his car dashboard & when he got home, on the way into the house, one started to ignite. He just got it to the sink & got it in water. Yes INC is, as JPeelen notes.

The caseless rounds in my collection used to be kept in plastic tubes with tops, I noticed some of the tubes discoloring & even slightly warping, and the powder/case showing discolor, on some rounds. So now all my caseless examples are now removed and do not seem to be going bad, or getting worse.

Couple of days ago I was looking through a collection outside in the direct AZ sun & some of the rounds were sitting in it for about an hour or more. When I touched them you would have thought they just came out of a gun.

Cook-off is a well known problem even with new powders being used. Although not the definitive answer to the post, exterior heat was a factor in the two instances noted above.

I know of one B-patrone that self ignited, it was stored inside a house, but the sun reached it through the window. I’ve also been adviced to be carefull with some “pregnant” old flare round. I keep those in a fireproof cabinet in my garage.