Another "Shelf Life" Post

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Nick_C_S

New member
I lived in central valley of California (Sacramento area) all my life. It's a very warm climate, to say the least. This made propellant storage a no-brainer. It must remain inside the air-conditioned confines of the house.

March this year, my wife and I escaped Kalifornia to the freedom of the great state of Idaho and moved into a newly built home. The climate here is much cooler :cool:. To my surprise, there was a little room, accessed from the garage, that is a small storage area below the stairwell inside the house. I call it the "garage pantry" - for lack of a better name. The instant I saw it, I knew that's where I'm going to store my powder; and did so.

I keep a thermometer in there and monitor it frequently. As it turns out, in the summer it gets a bit warm in there - approaching 80 degrees. So I thought it best to move the powder in the house - where it's a constant 76 degrees. Now that the cool months have rolled back around, I'm keeping the powder back in the garage pantry again.

At night, the outside air temp has been dropping deep into the teens (f). The garage itself is running in the very low 40's, creeping up to about 50 during the warmest part of the day. The garage pantry is 55 degrees during the coldest time of day, creeping up to about 62 in the afternoon.

And that's the real question: Is this temperature fluctuation at cooler temps better of worse for the powder than a constant warmer temp?
 
Not being an expert chemist, I don't think it really matters much. Powders SHOUJLD NOT degrade until after storage temps reach over 120F and more likely 140F.

As far as I know, powders also don't break down from cold storage, then returning to more temperate....

That being said, the individual powder and Lot# makes a difference. Some powder, made "poorly" compared to another might not last as long.

Storage that dips down to freezing or just below and back up to the 80s with the seasonal changes SHOULD NOT affect modern smokeless powders.

However, "should not" is not "WILL NOT" so be aware of that.
 
Cool and dry is what you want. I remember reading a post where the idea of keeping powder in the freezer was entertained. The main issue was moisture, but barring that, it had a crazy shelf life of a couple hundred years if I remember right. Due to the reduction in degradation due to the very low temperatures.

Basically heat increases the speed of chemical reactions, in this case degradation. Cold slows it down. So the question comes down to balancing, how warm for how long vs how cold for how long.
 
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All powder deteriorates all the time. That's why it has to have a stabilizer included in its formulation to neutralize the powder-destroying acids that results from nitrated constituent breakdown. As Shadow9mm said, what temperature does is affect the rate at which the deterioration occurs, and thus how rapidly the stabilizer is used up. Generally, there is enough stabilizer that the powder won't loose enough energy to cause serious deterioration of ballistic performance until after the stabilizer is gone. However, the rate at which it is consumed does go up exponentially with temperature, so favoring coolness is best. Once the stabilizer is gone, most powder rapidly weakens and starts to release corrosive acid in the bore. I had one coated with rust as a result of shooting some weakened powder loads.

There is also a phase some powders go through where the acids from breakdown attack the powder's deterrents faster than the deterioration costs the powder energy content, raising the burn rate significantly. This has burst a few guns. There was a photo of the remains of a Garand online that had actually had its receiver ring blown apart (very hard to do to that rifle) firing, IIRC, 1947 government ammunition. No idea what powder was in it.

Anyway, keep it cool and sniff it when you open it. At this point, having discovered two canisters of powder in my cellar that had gone bad, despite reasonable temperatures, I try not to load years ahead, instead shooting and replacing more on an annual basis.

The only other issue is humidity. Norma's manual shows burn rate changes with RH for all their powders. Desiccated powders can burn twelve percent faster than powder kept in 80% RH. They also show water vapor slowly makes its way in and out of cartridges and over a period of a year cartridges they equilibrate with outside humidity conditions. Their powders are shipped having been stored in, IIRC, 40%-60% RH. It's worth keeping in mind that load data from a powder company will reflect performance at their storage RH. Different powder storage conditions is one of several reasons different manuals have different maximum loads for the same powder.
 
I believe it was an old member here ( Slamfire ) who posted a quite detailed analysis of papers the United Nations ( UN ) wrote on there testing . I can’t even begin to quote all that he wrote . However I can give you my take away . Store in a dark dry place not exceeding 85* and the powder will do just fine . I don’t remember the exacts but it went something like this .

0 to 85* powder was relatively stable or slow to deteriorate. Every 20-ish* above that it deteriorated faster and faster to somewhere between 140 to 160* it only lasted a couple years . Keeping in mind these are just general numbers and not the exact study data .

Unclenick please correct anything thats needed but thats what I go by . Point being if my powder got to 80* I would not be worried . Also keeping in mind those test were done at a constant degree of heat , your little storage area isn’t even 80* all the time so imho you are gtg .

EDIT : found it

See post 14 here
https://thefiringline.com/forums/showthread.php?t=574938&highlight=storage+temperatures

cC9QVi.jpg
 
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IT is a bit interesting that the original gunpowder (black powder) doesn't degrade with age. Get it wet and it won't work, but dry it out an it will work again. There is no chemical interaction like there is with smokeless (nitro) powders, because black powder is a chemical mixture, NOT a chemical compound.

This is why one sometimes hears of muzzle loaders left loaded a century or more, going off when fired.

The chemical compound that is smokeless powder will break down with time. The specifics of its manufacture and storage conditions will have an effect on HOW MUCH time before it deteriorates.

I have seen smokeless rounds over a century old go off just fine, and also have seen rounds only a couple decades old fail because the powder broke down.

I still have some handloads I made back in the late 70s/early 80s that I expect are still fine, but I know the storage history of those rounds. What you get when you buy something like surplus ammo, is normally totally unknown.
 
Thank you for all the info folks. A knowledgeable bunch we have here for sure.

I'll keep doing what I'm doing: garage pantry in the cool months, in the house in the warm months.

sniff it when you open it.
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I always do. It's muscle memory at this point.

At this point, having discovered two canisters of powder in my cellar that had gone bad, despite reasonable temperatures
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I've had one. Ramshot Silhouette. Stored in the same environs as the others. I'm assuming it was a "one off" fluke. It also just so happened that it was the first propellant I used after the move from California to Idaho and I hadn't loaded in some 16 months. My sniffer was out of tune and didn't notice the "off" smell. It was mostly just dull smelling; not that "fragrant-chemical" (ether??) smell. Anyway, I brushed it off and loaded. Then, after loading, I noticed it caking up and sticking to a cotton tipped applicator as I was emptying the hopper. I knew then something was wrong and re-smelled - confirmed bad. I still shot the ammo - stuck bullet on round #25 - tossed the remaining 75.

I try not to load years ahead
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Me too. But mostly because over the years I've learned that my shooting style/needs tend to change as the years roll on. What ammo I shot a lot of this year, may be of little interest to me next year. But yes, it also has the advantage of not having to pull hundreds of bullets (I wouldn't) due to a bad powder.
 
It’s so hard to predict. Some survives decades of abuse and others go bad in a few years. I just pulled some Turkish Mauser rounds with split necks and the powder looked good as new despite being loaded in 1943. Now if only someone had taught the Turkish arsenal about annealing case necks…
 
I kept my powder (bought in the 1970's) in a garage in Northern Arkansas until my wife and I moved to Texas in the late-1980s where they were stored in our garage.

Of course Texas has such a moderate climate that Tanya Tucker once sung that she would "ride through all of hell and half of Texas".

After nearly 40 years of storage in 100 degree summers, the only powder that I owned that experienced any meaningful deterioration was Green Dot.
 
I'm a bit of a knowitall when it comes to this stuff after years of dealing-with-it in the military from Aberdeen to Bragg and decades of reading about it and talking about it with friends from Otterburn to Eglin .... and still, I learned something in this thread.

This is a cudos bump to my many fellow, knowledgeable, members of this community who participated in this thread and even some who contributed without even being here.
 
Metal god,

The one other factor is that the powders used by the military and most commercial makers are generally a single bulk lot made at the same time, which has the longest life expectancy. The canister-grade powders sold to reloaders require a more consistent burn rate than bulk lot processes can be relied on to achieve. That's an accommodation for handloaders because handloaders rely on books of recipes rather than owning pressure guns to determine charge weights for each powder lot, as the big ammo manufacturers do. To be valid with recipes for handloaders, the canister-grade powders are blends of old and new lots of the same powder type that happened to come out of the powder plant with different burn rates. This blending is often done using older lots that were held back because of their higher or lower-than-normal burn rates for the powder type, though that is not the only approach taken. Norma actually breaks up each new bulk lot to receive four different levels of deterrent coating. They then concoct a mix of those four lots to get the controlled burn rate. On the other hand, I doubt they toss out the leftovers that didn't fit in the final mix, and I suspect those get used in later blends that need them. Anyway, you can end up with a new lot of canister-grade powder that some portion of which is getting old. Since breakdown is initiated by whatever part of the powder mass goes bad first, this can pre-age your lot and cost you storage life expectancy.

Airborne Falcon, were you at Aberdeen when Humpy was?
 
powders used by the military and most commercial makers are generally a single bulk lot made at the same time, which has the longest life expectancy.
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Funny, I had just surmised this ^ on my own yesterday. Makes sense.

Which leads to the next logical question: How do us regular folk get ahold of any of this "bulk lot" stuff? I know it wouldn't be "cannister grade" and thus, the burn rate could vary quite a bit from what was intended (>3%), so extra care would be needed for work ups, etc.

Expectations of procuring such a product are low ;).
 
Every surplus military or pull-down powder you find is bulk-grade. But it's not new. So, you get together with about 500 of your closest friends and order a train carload of powder, all the while understanding its burn rate could be off target by a good bit. It's one of those inconvenient things.

Far easier is to find a lot of canister grade you like, buy a bunch and store it in heat-sealed freezer bags in a deep freezer. That will likely last centuries.
 
Unclenick, when the powder is stored in the freezer, should one wait to use it until it reaches room temperature? Does it weigh more or less in a frozen state?
 
heat-sealed freezer bags
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That ^ would make me nervy - to say the least. :p

cdoc42, here's the "not Unclenick" answer: I would wait for the propellant to reach room temp before using. And I don't believe it would weigh more or less in a frozen state, since the amount of mass is the same.
 
Unclenick,
I understand blending for consistency, my outfit did it with an entirely different product.
But are you saying that the powder company holds back powder long enough for its age to matter in the final mix? Hard to see how some 2020 powder in with fresh is going be a consideration. Surely they don't have 2002 powder sitting around to adjust with.

Can you explain why deteriorated powder is likely to pressure spike.
The usual signs of acidic smell, visible fumes, rust and dust come from a loss in degree of nitration. Looks like there is less energy available.
A post mentioned a stuck bullet which seems more likely.
 
Nick CS, I agree with waiting for room temp. But my concern is, even though I use my vacuum sealer for food, there can still be evidence of ice crystal formation; minimal compared to "saran" wrap first, and freezer bag with as much air squeezed out as possible, but I still can see it.
If there was "any" water formation in with the powder, it adds to the weight. I wonder if room temp is enough to cause sufficient evaporation.

As well, has anyone used a vacuum sealer in this fashion with gunpowder? Does the unit suck out any powder as it does with moisture?

I just thought of an experiment: take 50 grains of any powder, put it in a plastic freezer bag, squeeze the air out, weigh it (the bag adds weight),freeze it, then thaw and weigh it when it thaws and the outer surface is dry- without opening it first. Any increase in weight should be water accumulated during freezing.
 
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If using a vacuum sealer, I would not be sealing powder dumped into the bags. I would seal the unopened containers in the bags. As long as the containers are more rigid than the bags, the bags will be sucked down rather than the containers being expanded open by air pressure inside them. The reason for using heat-sealed bags is none of the zipper-type freezer bags I've seen make a real seal. They all leak at the corners. A vacuum, however, is only necessary to save freezer space by drawing the bag inward.

Yes, let it warm to room temperature before opening if you don't want condensation adding water weight to your charges.


Jim,

Slamfire had a post up some time ago about a Navy study (in the '60s, maybe) in which pressure in a tested lot of M80 ball went up from something like 48000 CUP to 72000 CUP after aging at something like 140F for a number of months (18, maybe). They concluded that in this instance, the acid radicals evolved from the deterioration of nitrocellulose and nitroglycerin had attacked the deterrents faster than the remaining nitrocelluose and nitroglycerin. The result was weaker (less energetic) charge, but one with a much faster burn rate. If they had kept aging it, no doubt it would eventually have weakened to the point the fast burn rate no longer mattered and the loads just seemed wimpy. So there's just an aging bad period that stats some time after the stabilizer is used up, at least for some powders. It may be that only some deterrents are vulnerable to this.

Regarding powder blending, I don't know the whole story, but I've had properly stored powder go bad twice before, and of course you see recalls occasionally for powder that has been going bad prematurely. There was a lot of N140 in the '90s that did, and some 4350 in the early 2000s, IIRC, and then, of course, all lots of IMR4007 SSC wound up being recalled. That powder has also been discontinued, so I am not clear exactly what went on there, whether is was an aging or an actual formulation issue or what. I can tell you one of the moderators on another forum has been involved in the business and says most people don't have any idea how much shifting of sources and other things go on. He said he's been at surplus powder auctions where he has been bidding against folks from Hodgdon. Especially during shortages, companies will do what they need to do to keep product moving.

The bottom line is there is no way to be 100% sure what you've got, so I have shied away from loading far ahead. Load for the season with canister-grade powder, sure. Load for the next decade? Not me. I've also had one lot of surplus ammo go bad on me, and don't expect to give that opportunity to another.
 
says most people don't have any idea how much shifting of sources and other things go on.
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The shifting of sources and formulations we DO know about is bad enough.
"Buy Acme #2995, flagship of our line for 50 years. Be sure to use only current data."
"Why? Is it 2995 or not?"
 
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