AR15.Com Archives
 Cold weather & ammo storage?
MontuckyMan  [Member]
1/28/2007 7:09:50 PM EDT
I recently moved from an area were the weather is not extreme, but now I am in Montana where it gets pretty cold. My question is does the cold weather effect my ammo stored in ammo cans on a pallet in the garage in a negative way? I'd hate to ruin thousands of dollars worth of ammo. Thanks in advance

Oh yeah by the way I am building a POF so when I get it I'll post some pics
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deadboi77  [Team Member]
1/28/2007 7:59:52 PM EDT
Good question.As I would like to know as well.Since more than likely,`ill have to be moving some of my ammo stash to the garage and/or polebar.More than likely,the polebarn as my garage tends to get pretty damp.
Charging_Handle  [Member]
1/28/2007 8:22:32 PM EDT
I worry much more about extreme heat (i.e. the temps reached in car trunks on 90 degree days, garages or other storage buildings with no air conditioning, etc) than cold. OTOH, I have never really had to deal with extreme cold either as far as my ammo storage, certainly not sub-freezing temps. I keep most of my ammo in .50 caliber ammo cans spread out across and stacked on the floor of my closets. If you don't stack it too high, the closet will still function fine for hanging clothing and you end up using the floor space for ammo storage, whereas otherwise you'd just end up stacking a bunch of worthless junk there.
MontuckyMan  [Member]
1/28/2007 8:35:12 PM EDT
I'd love to keep the ammo in the closet, but no room. Between my stuff and my woman's leaves me no room for closet storage. I used to keep it all in the closet for years and I have never had a problem. Now it is in temps down to -30 and lower sometimes. Any other replies from people living in cold weather climates would be great. I figure at least it's off the cement floor on the pallets. Thanks
MontuckyMan  [Team Member]
1/29/2007 7:53:26 PM EDT
chrome1  [Team Member]
1/29/2007 8:28:04 PM EDT
I don't know about long term , but I've had ammo in the trunk
of my car for over a month in temps that ranged from +20 to -20
without any ill effects .
Ryan1021  [Member]
1/29/2007 9:53:19 PM EDT
The ammo I stored in the garage in ammo cans during last winter fired without a problem in the spring, summer, and fall. Now I am sure Southwestern Ohio probably does not get as cold, but we do get fairly cold weather here.
WMHM4  [Team Member]
1/30/2007 4:23:16 AM EDT
as satated above I don't see cold weather being a problem but I would be more concerned with moisture from hot weather.
pyro6988  [Team Member]
1/30/2007 4:53:29 AM EDT
it will be fine as long as it stays dry.
Verk  [Team Member]
1/30/2007 4:59:37 AM EDT
I believe the key to extended ammo storage is a somewhat constant temperature and low humidity. I have shot ammo that has been stored in a constant environment that was over 25 years old with not a single misfire.

I think short term, it will not be a problem but over time it very well could be an issue. With ammo prices nowadays, I would consider storing as much of it as you can in a somewhat controlled environment if at all possible. Good luck.
ranchhand  [Member]
1/30/2007 2:46:42 PM EDT
I bring mine in, spread it out, leave it inside for a couple of days to dry out any moisture (humidity is very low indoors in the winder) then repack it in sealable ammo cans. It can take normal garage extremes then. I packaged some this way 15 years ago that is still bright without any tarnishing, it looks new.
MontuckyMan  [Team Member]
1/31/2007 9:36:02 AM EDT
Thanks for the replies all!!

We'll for now it's going to stay in the garage, since I have no other place to store it at the moment. I'll keep you all posted on the long term storage in the cold here in Montana.

KnobCreek  [Team Member]
1/31/2007 9:50:37 AM EDT
I had this "article" saved on my computer from awhile ago. Can't remember the source but I believe it touches on much of what's been recommended.

"First of all, I'd like to suggest to one of the moderators that this entire thread get moved over to the Weapons section, where I think it is more appropriate.

This question of ammunition storage is a good one. Thankfully, there’s been some good research done as well. Here’s the short version: Modern fixed ammunition has two primary enemies: heat and moisture. Of the two, moisture is generally the more damaging. Cold alone appears to do relatively little permanent damage to ammunition, although cold conditions often involve moisture (including condensation within the cartridge itself), so other than in a laboratory, it’s difficult to comment on cold without addressing moisture as well. The most vulnerable part of a fixed cartridge is the primer, although extreme temperature swings can affect the burning rate of certain powders (more on that in a minute).

The Bad News: Improper storage of all that ammunition you’ve horded can make it worthless.

The Good News: Modern ammunition produced in the United States is incredibly well-made, and when stored under proper conditions one could easily expect a shelf life of 50 years, or even double that.

The Bad News: You probably haven’t stored your ammunition in an ideal fashion.

The Good News: Ammunition made in WWII is routinely available, and most of it at least ignites just fine (more about this point later as well). This stuff generally wasn’t made as well as modern US-manufactured ammunition, and it’s still functioning sixty years later.

The Bad News: If you’re buying surplus ammunition, you often have little idea how old it is, and virtually no idea under what conditions it was stored.

The Good News: If you adhere to the precepts of ammunition storage outlined here, you’ll die of an infarction long before your ammunition goes bad. Which means after you croak, when I swoop down on your estate sale and buy up all of your carefully hoarded ammo for five cents on the dollar, I’ll be getting the deal of the century.

* * * * *


Modern ammunition is really just a cocktail of chemical compositions, and as with most chemical reactions, heat speeds them up and cold slows them down. This is especially true of degradation. What this means is that primers stored in hot (120-degree F-plus) environments pretty consistently show a breakdown of the priming compound, sometimes after as little as a year. Sure, it may be butt-freezing cold in your little slice of the world on this January morning, but 120 degrees isn’t as uncommon as you think, especially since we’re not talking about 120 degrees outside air temperature, but 120 degrees where the ammunition is stored—think hot car trunk, an uninsulated attic or warehouse, or a steel shipping container sitting on a flatcar for a couple of months or a railroad spur in the southwest. (Not an uncommon occurrence—manufacturers know that renting a flatcar and parking it on an unused section of track is a lot cheaper than renting warehouse space.) Reports from Iraq show some relatively serious degradation of 5.56 x 45 ammunition in less than a year. It’s easy to see a quantity of this making its way back to the States and finding its way onto the market, too.

As noted, extreme cold per se appears to have a relatively small deleterious effect on ammunition, but the concomitant moisture does. Ammunition fired while it is very cold often ignites perfectly, but shows a not-insignificant drop in velocity. Ammunition merely stored in a cold environment and fired in a normal temperature typically reverts to its standard velocity

Tropical conditions are another story, and probably the most deleterious in terms of ammunition storage. As air temperature rises, the ability of that same air to hold moisture also rises—that’s why it’s so humid in Panama during the summer, but so dry on a 14,000-foot Colorado peak in December. So, under tropical conditions, you have both high heat and potentially high moisture.

As noted, most modern propellants uses in the US are relatively temperature stable in terms of performance, but this is not always true, and certainly wasn’t in the past. When the British were loading cartridges with Cordite in the fin de siècle period when the sun never set on their empire (cue the Bonzo Dog Band’s Hunting Tigers Out In Indiah), those rounds would produce a much higher pressure in hot, tropical conditions. This became a real concern when a rifle was chambered for something like the .375 Holland and Holland Magnum, or one of the British .400 or .500 big bores. A “tropical” rifle was built extra-strong to handle the loads; today, Ruger still offers a “Tropical” in their magnum Model 77 lineup. “I say, J.O., jolly good!”


This is much easier to understand. It destroys primers, and corrodes brass. Under severe conditions, it may even compromise the powder. All bad. This doesn’t have to be standing water, either; just think humidity over 60 percent.

Ideal storage:

Thankfully, both the NRA and the military, as well as the ammunition companies, have done a lot of research here, and it’s pretty accessible. A year and a half ago, I cited some test on the subject, which I’ll reproduce here; it’s really the best-case scenario:

The method the military and ammunition industry use for long-term storage of ammunition is very old and very simple. Make a concrete bunker with walls about a foot thick. Then cover the whole thing about a yard deep with dirt. This construction is called an "igloo." The igloo produces a remarkably constancy in temperature and humidity inside, requiring neither power nor adjustment. Using this technique, modern small-arms ammo may be stored for 40 or more years with no material degradation. Conversely, ammo "stored" in a hot car trunk may be dead as a mackerel, or wildly inconsistent in a single summer. However, not all of us have an "igloo" handy. Given even moderately consistent conditions most modern ammunition components are fairly resistant to degradation in the short run, say 10-15 years, absent high temperatures and/or constant temperature fluctuations.

To hit the high points of home storage very generally

1. In general, it is the PRIMER that you are worried about. Absent excessive high temperature and/or humidity, modern smokeless powder is very resistant to degradation in storage. As an interesting aside, corrosive priming compounds commonly in use have longer storage lives and are more resistant to degradation than comparable non-corrosive priming compounds.

2. No matter where you store ensure there is "dunnage" (i.e. 2x wood) under and between each layer stacked. Also ensure there is air space between stacked cases on the same layer. These provide air circulation, which is crucial.

3. Humidity--Drier is better, but in sealed cans will make little difference if dunnage and air space are maintained. The ammunition should be packed with a desiccant. You can purchase a commercial product or go the "do-it-yourself" route. Go to any construction site and ask the straw boss if there are any broken sheet rock boards around or some wallboard scraps. There will usually be. Sheet rock is gypsum and hydroscopic. Get a few pieces and cut them to about the size of a deck of cards square. Cook them in the oven at about 200 degrees for a few hours to drive the moisture out of them, then put one in each of your ammo cans. The piece will absorb what little moisture there may be in your ammo can giving you a nice dry environment.

4. Temperature--This is a big one with lots of details. Good ammo is like good wine. Both like a constant, even temperature around 65 degrees F. The constancy of temperature is more important than the temperature itself. (This is a dandy excuse to build a wine cellar to store both.), And, as a wise man once said, "you can never have too much of either."

For short-term storage of general-usage ammunition, the most important factor is to keep the ammo out of excessive heat--say over 85 degrees. Excessive heat degrades ammunition. Ammo stored in car trunks is the most common victim here. Low temperatures do not harm ammunition per se. What degradation may occur is caused more by repeated temperature fluctuation than by the cold. (As an aside, double base powders can perform erratically when USED in very cold temperatures, but this is not a function of storage.)

At this point we probably should explain what we mean by "degradation" If you're storing MG ammo or "rattle battle" ammo, for a few years, the garage should suffice nicely, given the constraints above. The standard deviation of the velocity may go up slightly, but I suspect you will not notice a thing. On the other hand, if you are storing match ammunition, I'd recommend keeping the stuff in a place with a more even temperature. The bedroom closet, where the temperature stays nice all year, for instance. With something as precise as match ammunition even a little degradation could be of consequence.

Invest in a "min/max" thermometer that shows both the minimum and maximum temperature recorded. They run 10 bucks or so. Check your storage area monthly for signs of excessive temperature (check the min/max) or other degradation (rust on cans, etc.). There are no magic procedures. Just remember that equipment respected is equipment that will be reliable."
ranchhand  [Member]
1/31/2007 10:42:38 AM EDT

Originally Posted By MontuckyMan:
Thanks for the replies all!!

We'll for now it's going to stay in the garage, since I have no other place to store it at the moment. I'll keep you all posted on the long term storage in the cold here in Montana.

Right now is a perfect time to repack it. When the dewpoint is 0 or less outside (right now it is 5 here and I'm in TN!) the humidity inside your 65-70 degree house is super low.

Bring in a small quantity (1 ammo can or so) spread it out a little so it gets decent air circulation, and repack it tomorrow. Repeat with a new batch until you're done. Alwys mark the can so you don't have to open it to look. Keep it sealed until needed.
MontuckyMan  [Team Member]
1/31/2007 2:06:59 PM EDT
Well that will take some time to do, but I will start on it tonight. At least it is usually very dry in the area I live. Thanks all
ranchhand  [Member]
1/31/2007 3:41:53 PM EDT

Originally Posted By MontuckyMan:
Well that will take some time to do, but I will start on it tonight. At least it is usually very dry in the area I live. Thanks all

Even better reason to do it now. I got 1560 rds yesterday and spread it out on the table. This morning, I packed it in gasketed ammo cans and expect it to look new for 10 years or more.
ar_mcadams  [Team Member]
1/31/2007 8:37:39 PM EDT
the more ammo in the can the less room for air.
MontuckyMan  [Team Member]
2/1/2007 8:23:57 PM EDT
yeah i have my cans packed to the brim

and BTW i really like those 40mm ammo cans. very good quality and rubber seal.
Ohio47Woodsman  [Member]
2/2/2007 3:07:06 AM EDT
Knob--Thanky! Good piece.

Goes to show ya--you can even teach this old dog new tricks!
Ragin_Cajun  [Member]
2/2/2007 5:10:41 AM EDT
I've heard of ammo and explosives deteriorationg from prolonged exposure to heat, especially combined with humidity, but I've never heard of it being affected by cold.

Granted you won't get as much velocity if firing in extreme cold because chemical reactions of almost any sort go faster with heat.

If I had to go out on a limb, I'd say that the cold is actually helping keep it "fresh" since explosives are generally organic compounds IIRC.

ETA: Looks like KnobCreek said everything I did, better than I did.
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