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Can Gunpowder Spontaneously Ignite? Yes! Long-Term Powder Storage Hazards

It's quite rare, especially with modern powders, but it is possible for gunpowders to deteriorate over long periods of time and self-ignite. Here's one case that happened and how to prevent it.

Can Gunpowder Spontaneously Ignite? Yes! Long-Term Powder Storage Hazards
Best practices in storing powder must be followed, and regular periodic checking of stored powder is advised. Dispose appropriately of any that has gone bad.

If you’re a serious reloader, you likely have a dozen or more propellant bottles near your loading bench. A friend of mine had 100+ one-pound containers (77 still factory sealed) carefully stored in his climate-controlled shop. My inventory includes a similar quantity that I’ve accumulated during the 50+ years I’ve been handloading. Let me strongly remind you: Only your acute awareness and rigorous periodic surveillance can avoid a hazardous event. Small arms propellant—even when carefully stored in a safe environment—can chemically deteriorate and, worst case, spontaneously ignite. Fortunately, I’ve never experienced that type of frightening event, but my brother did. Recently, he and his wife were sitting in their family room watching TV. Suddenly, from behind his recliner, there was a loud “WHOOOOSSS!,” and a huge flash of fire erupted from the stairwell near the inside exit to the garage.

He jumped up and was able to open the door and literally kick the remains of two caddies of shotgun powder onto the concrete floor of the garage. Quickly filling a large bowl with water, he doused the smoldering pile of powder and plastic. With the immediate danger under control, he scooped the residue into a larger bucket of water, and his wife used wet towels to snuff out smoldering patches of carpet. This dramatic episode began several weeks earlier when he sold two sealed four-pound containers of shotshell propellant to a friend. A few days later, the fellow opened one of the containers and immediately noticed an obnoxious smell. He loaded a few rounds anyway just to see if the powder was still usable. After firing a few “bloopers,” he promptly reported the problem to my brother. My brother called me to discuss the situation, and we speculated about what could have caused the powder to deteriorate. He had kept another partial container of the same type and vintage (approximately 20 years old), and it seemed to be okay. He made arrangements to return the friend’s money and retrieve the powder.

Several weeks later, my brother picked up the powder and instead of going straight home, he served volunteer duty at a local golf course that afternoon. It was August, so his car (with the two plastic jugs of suspect powder on the back seat floor) sat in the sun with the windows closed for about five hours. When he did get home, he took the two containers into the house and set them on the stairwell step. The exciting events I just described occurred a couple hours later. The fire department responded promptly and surveyed the situation. One of the firemen pointed out that the filter in the AC return duct located in the ceiling above the stairwell was mostly missing. Soot residue was all over the house. We wanted to know what caused the event, and after searching several web sources and talking with some industry contacts, I concluded the SAAMI publication on powder storage offered the best explanation of what likely happened. Its statement goes like this:

“Although modern smokeless powders contain stabilizers and are basically free from deterioration under proper storage conditions, safe practices require a recognition of the signs of deterioration and its possible effects. Deteriorating smokeless powders produce an acidic odor and may produce a reddish brown fume. (Don’t confuse this with common solvent odors, such as alcohol, ether, and acetone.) Dispose of deteriorating smokeless powders immediately. Check to make certain that smokeless powder is not exposed to extreme heat as this may cause deterioration. Such exposure produces an acidity which accelerates further reaction and has been known, because of heat generated by the reaction, to cause spontaneous combustion.

“Never salvage powder from old cartridges and do not attempt to blend salvaged powder with new powder or attempt to blend two types of powder to make a ‘custom’ blend. Do not keep old or salvaged powders. Check old powders for deterioration regularly. Destroy deteriorated powders immediately.” I reload, read, and just hide out sometimes as well as store all of my reloading components in my man cave. It’s a scale version of my house, and it is climate controlled. I’ve sporadically checked my powder inventory and have discovered only two bottles of bad powder in the past 50 years. After this mishap, I promptly inspected every container. It took a while, and I didn’t find any bad powder, but as the photo indicates, there were quite a few old and/or salvaged propellants that I really should not have accumulated. I related the incident to David Emary, contributor to our sister publication Guns & Ammo, and he shared his insight into the apparent cause of the event. The heat exposure in the car likely tipped the scales to rapidly accelerate further chemical deterioration, which progressed until a keg spontaneously combusted.

Fortunately, he followed my prompt action plan and checked his powder inventory. He called me later and said he had found a partial can of powder that was bad and, just like I’d done, disposed of it by scattering it around his lawn. It’s expensive fertilizer, but it’s better to be safe than sorry! Modern propellants are manufactured by skilled personnel following proven processes in well-equipped and quality-controlled facilities. If you store your powder in a cool, dry place, it will likely last a long time. However, things can inadvertently happen during manufacturing, storage, and handling before and after you acquire the product. The shelf life of propellant can be compromised—sometimes significantly. Set up a schedule to check your inventory and don’t hoard excess quantities of propellants. I know they’re expensive and buying bulk can be economically attractive. However, neither you nor I need the type of excitement my brother experienced!




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