While avoiding humidity is pretty much a universal theme on the topic of long-term ammunition storage, there is a lot of directly contradictory information when it comes to heat. I’d like your input if you have any experience or observations in this area.
I bring up this topic because my brothers and I will probably have to store a large quantity of ammo in a barn for a few years (basically, Mom wants the guest bedroom closet back). Nebraska summers can be fairly brutal, and the inside of a barn can get very hot. Will our ammo be okay (will be in ammo cans)?
The generally very informative Ammo Oracle at AR15.com has this to say:
The three primary killers of ammo are heat, moisture, and chemicals. Excessive heat will break down both the powder and the primer compound over time, causing erratic ignition and velocities.
Military guidance on how much heat is too much heat doesn’t offer much. Department of the Army Pamphlet 700–16, THE ARMY AMMUNITION MANAGEMENT SYSTEM for Logistics, does not list any temperatures, noting only that:
In general, ammunition must be protected from moisture and should be protected from temperature extremes when feasible.
Department of the Army Pamphlet 385-65, Ammunition and Explosives Safety Standards, says in Chapter 2, Field Storage of Ammunition:
When standard magazines are not available, buildings used for AE [ammunition and explosives] storage must afford protection against moisture and excessive changes in temperature and have means for adequate ventilation. . . The AE containing explosives or combustibles (such as, black powder, tracer composition, or pyrotechnic mixtures) that deteriorate rapidly in damp or high temperature environments should be stored under the best cover available.
And MARINE CORPS ORDER P8020.10A, MARINE CORPS AMMUNITION MANAGEMENT AND EXPLOSIVES SAFETY POLICY MANUAL, does not refer to heat or temperature at all, in regard to ammo storage.
Anecdotally, some say heat is bad, others note they’ve used ammo stored in very hot bunkers with no issues. Various old and/or surplus ammo from the 1950s or earlier not stored in cool conditions that still functions, and hand-loaded .223 ammo in a VA attic for ~25 years, working fine.
You can find dozens of forums or blogs that say one other, but I haven’t seen any actual studies. From a common sense perspective, seems like heat might affect ammo since it affects food and many other chemical compounds. But with a little more information, a lot of real-world examples seem to point to heat not mattering much, which might alter what passes for common sense.
From my personal experience (more anecdotal evidence), I’ve seen Conex boxes in the desert storing U.S./NATO ammo, and have personally used ammo stored in hot humid conditions for long-term with no problems. I’m talking shot shells (some old enough to be some sort of cardboard or thick paper rather than plastic), .22S/L/LR, various old surplus calibers (some with slight corrosion), etc. not in ammo boxes or with AC during the summer, for decades.
I’m leaning towards heat doesn’t matter as long as humidity is controlled.
What say you?
I haven’t ever heard anything about heat. I don’t think it is an issue.
Heat can break down the nitrates I believe. If it isn’t that particular ingredient it is one of them or several depending. Anyway the first problem it produces from what I have read and been informed of is that it changes the actual burn or basic reaction differently depending on the type of powder you are using. Black powder can be made inert or can also be made stronger depending on who you talk to. The smokeless modern powders can have their qualities changed, some can develop more pressure some less. The same with primers.
A couple of us were having a discussion about this very topic not long ago at the gun club and the local reloading guru we all go to for his expertise explained it more or less I did above. He also added that heat was much more of an issue in years long past with older powders and effected cartridges with powder loads that didn’t fill the cases much like HP-38 in a light load which leaves a lot of space unfilled under the bullet.
Heat will also cause lead and especially non-jacketed bullets to begin breaking down faster and getting that white residue on it as it oxidizes. That could effect FPS and leave some nasty stuff in the bore.
Just some mostly second hand info. I have nothing printed to back this up so take it as you will. I also have about 100 rounds of .303 brit that has been in the trunk of my car for going on 3 Summers and it appears to be just fine after gaining temps of I would bet 120 degrees or higher in there.
Seems to me like there’s quite a few people in very hot parts of the world killing each other with very old ammo and guns. 30 or so people still get killed every year in France from leftover munitions from WWI & II, mostly farmers plowing fields.
I wouldn’t worry about it.
I would say that Heat don’t matter much.
A good example would be the weapons caches in places like Angola or Mozambique, where they used to bury the stuff for storage purposes and it seems that AK-47 ammunition can endure hot season buried and would fire fine, unless the casing is rusted away.
I would suggest an experiment, but ”cooking” rounds is dangerous and I don’t think any performance loss from heat would justify it
Retired 55-series (Ordnance Corps) soldier here. Worked for several years at an Army ammo depot, tearing down WW II and Korean War munitions for recycling and disposal when testing showed the stuff was no longer serviceable even for training uses.
The Ammo Oracle is 100% correct.
Heat is the single worst thing you can expose ammunition to. Proper packaging can take care of humidity issues, but heat will accelerate problems with residual acids in smokeless powders and problems with primers (particularly non-corrosive primers) going bad.
A summer or two in a barn isn’t going to kill ammo. But it’s going to cut short its useful life. Good ammo won’t go bad overnight, but it will become less reliable and less accurate. Eventually you’ll start having problems with dead primers. If the powder wasn’t completely washed of the acids used to produce the nitrocellulose and a proper amount of neutralizing agent added, you’ll start to see a fall-off in accuracy as the powder breaks down. Possibly with corrosion of the interior of the cases that can lead to case failures and possible damage to the weapon and/or shooter. This is a bigger problem with steel cased ammo than with brass cased ammo. There’s a lot of WW II German 8mm out there still, much of which is so corroded on the inside that it’s very unsafe to fire.
The Pakistani .303 British that has such a terrible reputation is an example of poorly stored ammo that many people have encountered. Right now there are a lot of people complaining about corroded German 7.62mm NATO, though the problem there looks to have been caused by residual acid in the cardboard boxes inside the sealed battle packs.
A quick test that can reveal problems is to sniff the ammo when you open the container. If it smells acrid, that’s a sure sign of problems. A solvent smell is normal. Red fumes, corrosion of the interior of the container, visible corrosion of the cases are all signs that there is a problem.
I was thinking the same thing on the AK ammo. I just bought some 7.62×54 from 1971 in a tin can. I’m sure it was moisture proof, but I doubt in all those years it never got hot. It’s been shooting great – no misfires yet.
When you go to old colonial homes they would dig a little pit in the floor of a small closet in their kitchen to keep their butter cool. Once you dig a certain point below grade you get to a constarnt temperature. Of course in a lot of places the problem is getting below the permafrost level which is why they tend to build cellars up North. Once you have to dig 6 feet down to get below the frost level, you might as well go a little further and get yourself a basement.
Under a roof, I suspect the permafrost issue is not going to be a problem most places.
Earnán,
Thank you for posting. That’s what I was afraid of. The stuff we are putting away for longer term is mostly brass cased, non-corrosive (except the 7.62x54R in spam cans) – .22LR, 9mm, M193, M855, and .30-06. I guess we can pack it in ammo cans and put it under the house, which shouldn’t be more than ~100F in the summer, I think.
I don’t know my away around the right Army manuals – do you have a reference? I understand if it’s experience over documentation, seen that enough.
I served the in the Marine Corps from 2006-2010 as an Ammunition technician in 29 palms CA “the middle east of the U.S.” look up the temps they get I experienced 120’s. I have literally dealt with every type of ammo from small arms 5.56mm to High Explosives (frags, AT-4’s and HiMars) I can tell you right off the bat that your ammo needs to be in some sort of ammunition container (ammo can). That is sealable and water proof, other than that heat will not affect most of today’s ammunition items and those of yester year, we were still dealing with dynamite from the 40’s. We consistently stored all types of ammo in the sand uncovered in the direct sunlight for months to even lengths of a year. We never stored any longer than that because it would get pushed out faster than needing to store it for longer. If you’re storing it in a barn that will be covered in shade and in ammo cans then you should be more than fine with long term storage of your ammunition I would recommend adding a tarp to keep more moisture away from your stack. It takes a very concentrated and high amount of heat to ignite the powders in rounds so outdoor storage is ok so long as they are in those approved containers. Hope this helps you out.
If you really need technical awnsers the NAVSEA OP 5 VOL 1 is called the ammunition saftey bible for a reason and most pof the safety questions you will have can be awnsered by this publication
Heat is bad for ammo, as it is for a lot of things. However, I have small pistol primers that were bought in the mid-seventies that still work fine, and other primers, rifle, large pistol, etc, that work fine. This was stored in a garage for many years and in a bedroom for many years. The only time I have ever had problems with old ammo was years ago when I had some .22LR stuff about ten years old. The Florida heat (we did not have air-conditioning) must have ruined the primers. Most of them fired, but about 3% did not.
I have reloaded since the early seventies, and some of my components were bought back then, yet still work fine. The oldest powder I have I am thinking should be thrown out by now (mostly small amounts left in eight-pound cans), but the primers are fine for target shooting and training. The old powder could be kept in small containers in my backpacks for fire starting, so I hate to throw it out for fertilizer in my garden.
For long-term storage, ammo can be sealed in containers and buried deep enough the temperature will remain constant year-round. In Florida, I think that would be about 78 degrees. Stored that way, ammo can last a lifetime. I have WWII ammo that is still reliable, but probably not as accurate as it was decades ago. This ammo has mercury primers, though, and they seem to last forever, while non-corrosive primers do not last as long and are not as consistent in cold temps. All of my long-term storage ammo is buried in PVC pipe. The rest is in military ammo cans in an underground storage room that has been sealed from ground moisture and the hatch also sealed when closed. Otherwise, condensation will form in the underground room. I try not to open it except on cool winter days when the humidity is low. This is where I keep a lot of my long-term storage food also.
I have been inside some ammo bunkers at an old navy base that were built underground. They were dug about four ft deep and the concrete storage vaults built then about six feet of dirt was piled on top of them. The temperature was very cool and was pretty constant the year around.
Ammo stored in a hot car trunk can produce higher than normal pressures too. I reload my ammo in thousand round batches and store it in plastic coolers. I think consistant temperatures insure consistant results.
JD
Ryan,
Thanks for the info. I’ve also seen ammo stored in the sand, but like you say, it wasn’t really there long-term as it was used.
What my brothers and I plan on doing is putting a lot of ammo purchased this year in .30 and .50 cal ammo cans, and storing it away for at least five years, or until TEOTWAWKI, which ever comes first. If five+ years comes first, we’ll start rotating it out.
Talking about a few tens of thousands of .22, a bit under ten thousand 5.56mm (XM193 mostly, with a smaller amount of M855, other brass-cased stuff, and some Brown Bear soft point 62 grain), a few thousand 9mm, a couple thousand 7.62x54R (Eastern block surplus, corrosive, already in spam cans), and smaller amounts of other calibers/gauges. Been in an ammo buying frenzy lately.
We’ll pack it in the ammo cans over the holidays while humidity is very low, and use some desiccant. If it goes under the house, we’ll cover the stack of ammo cans with a tarp and be done. If in the barn, they’ll be stacked in a wooden tri-wall container with a lot other stuff on top, and the plywood side will be screwed on.
Like my net searches, advice in comments is contradictory. While it seems good 5.56mm will be fine for a couple years of hot summers, I wonder about five, ten or more years. It may still go bang, but how much power and accuracy will be lost, if any? I wonder if modern 5.56mm is more resistant than the ammo produced decades ago, hence the difference in opinions from different generations?
If you go with the under the house option, then that will be the best thing to actual earth covered magazine, and your best bet for long term storage for your ammunition. A note from my experience in the four straight years in 29 palms I can tell you we had the same stack (LOT #) of ammo spend time outside and inside the magazines for the entire time I spent there since it was just not being used by the Marine Corps I think it was .45 if I’m not mistaken. Your barn option also sounds solid since you stated it will be sealed further protecting it from additional heat and the environment. I can tell you that it is from my experience with the “newer” generation of ammunition that it is extremely durable against time and weathering. I’m sure the manufacturer will have more information as the estimated service life for the specific ammo you need. To add both your options are solid I would try for the under the house and earth covered to prevent the most effects of weathering. Hope it goes well for you.
Ryan,
Thanks for the follow-up. We’re still undecided. Under the house would be much cooler than the barn, and a less obvious place for criminal to potentially look. But burying it there isn’t an option as it’s not earth but stone. Something else I thought about was the rare occasion a service worker needs to get under the house (e.g. to work on AC vents, Direct TV cabling, etc.). A large number of ammo cans (or a bunch of something covered with a tarp) might attract attention. We’re still trying to decide what to do.
Here’s a couple of thoughts for you. One, split up your stash so if the house or the barn burns down, you don’t lose it all. Two, for under the house, store your ammo cans in old boxes labeled “car parts” or “Christmas lights” or something else very mundane and uninteresting, and actually put a thick layer of these items on top of the ammo cans so any curious lookers will only see the junk they expect to see. Three, for the barn, use an old chest freezer, the insulation will buffer the temperature swings. Four, pile some heavy stuff on top of the chest freezer like an old engine block that no one is likely to want to move to look inside an obviously old broken freezer. Five, is there anywhere you bury the freezer which acts as an insulator and water protection, then park an old car or farm implement on top of it to mark the spot and protect it? Or do the same thing with a cistern or septic tank, then you would actually be below the frost line. Good luck! SG in Virginia
Extreme heat can be an issue if the inside of the can reaches a certain temp.. then your looking at the possiblity of a cook off. The Army does havde policies.. but not directly in Regs…You find them in Post Safty Policies. Just stack some pallets to creat 6 in air space underneath. If outside…add a tarp that will give 1 foot of airspace above, shaded on two sides, and the same 6 in off the ground. You won’t have problems in a barn. No direct sunlight to bake your ammo cans. It is an issue down at Ft. Bliss… but inside buildings, no. They keep it cool there. It’s just when outside in direct sunlight.
I am no ammo expert and respect the opinions here but in my own experience I have never had a problem with ammo stored in a hot place. I live in the God-forsaken desert. Have stored ammo in my garage and in my truck. Recently cleaned out my truck and found ammo that had to be 7-8 years in the blazing heat of the toolbox on the truck. 9mm, .223 and some birdshot for the 12gauge. All fired without a hiccup. Have fired old 8mm from just post WWII. God only knows where and how it was stored out here. Fired just fine. Just sayin’……
I think to have a cook-off of ammo in a can one would need to have it in a black can and positioned for maximum sun exposure. Even then I’d have to see it to believe it. ‘Course I’d rather not be there……
I agree with those that say heat isn’t going to ruin your ammo. I’ve stored it for a decade in a hot shed in ammo cans. Whenever I take some out to use it works. I’ve left it in ammo cans outside for a decade and it works. As long as you don’t get it wet it’ll probably outlive you. What more do you need. I like the idea of splitting up your stash just to guarantee against a fire or a ripoff. You can bury it if the water table is low. Put battle packs in a plastic cooler sealed with silicon sealant. It works.
Well I live in the desert southwest . If your going to store ammo outside of a house , and a barn qualifies as outside . I would build a cement vault . Concrete is cheap and it drops the temp quite a bit if you build it as an underground vault . That works perfect around here . It also protects against fire . All the commercial fireworks companies store things in this way around here . If you live in the east . you will have to be careful about mildew .