Ammo For Sale

« « Making the switch | Home | The American Revolutionary Era Origin of the Second Amendment’s Clauses » »

The experiment begins

We gun nuts argue over whether or not storing magazines loaded affects spring reliability. One the one hand, some us believe that the storage itself isn’t an issue but that the compression cycles cause most wear of magazine innards. Others think that long term storage isn’t good for your magazines. Looking through some stuff, there was this old magazine for a Sig P220. By my calculation, that magazine has been stored loaded at full capacity for at least 13 years, probably longer. Trouble was, I no longer have a Sig P220. But I knew someone who did and I sent it to him. Dirt notes that it’s an old school zipper magazine. Well, he’s going to take it out and run it through its paces and see if the spring still springs. Should be interesting.

26 Responses to “The experiment begins”

  1. mikee Says:

    13 years is a good long term test.

    I recall reading in a Cooper’s Corner from Guns magazine that a Schmeisser 9mm subgun from WWII was found in a wall of a German house, with loaded magazine. The police took the gun away, and upon testing found the gun ran just fine with the loaded mag of ~40+ year old ammo, and ~40+ year old compressed springs.

    Stories of this sort give hope to all those who buried their AK clones in PVC tubes back in ’94, and still can’t remember where exactly.

  2. Jeff Says:

    sounds like an excuse for you to buy a sig p220

  3. Tam Says:

    Some magazines are more susceptible to long-term storage than others. A lot has to do with design.

    Most are fine.

    Glocks can kill a spring because getting the extra round or two in there was more important than being able to store the mag fully loaded. (A Glock mag spring gets crushed pretty flat when full.)

    With alloy GI AR mags, a fully loaded one can spread the feed lips and is also very hard to seat with the bolt forward, which is the reason for the whole “download two rounds” thing there.

    Wilson 47Ds are notorious for killing springs if left loaded with eight rounds. Most any other 8-rd 1911 mag would be fine (slightly longer tube and different follower results in less compression of the spring.)

    Those are the three types of mags I know of off hand where there is some validity to the “long-term storage” thing. Other than, I can’t really think of any that are known for problems.

  4. Jay G. Says:

    13 years? Piker.

    Last month I shot a 15 round M1 carbine magazine that had been loaded for at least 30 years. I’ve had it in my possession for 17 of those years; the remainder it was in my grandfather’s possession. He didn’t shoot much in his 70s, and considering the ammunition was date-stamped to the 1950s, I suspect that it was original…

    Compression fatigue is a myth. It’s loading and unloading that causes the springs to wear.

  5. JDS Says:

    My prediction: (BANG)x8, and an utterly uneventful range session.

    Not only do I play an engineering on the internet, I am one in real life.

  6. Tam Says:

    Jay G.,

    Compression fatigue is a myth.

    Please send me your snail mail address. I have some dead Wilson 47D springs to ship you.

    Rather say “Compression fatigue outside of a very few poorly engineered cases is a myth.

    And as far as “loading and unloading” goes, see your valve springs, which are compressed and released more times backing out of your driveway in the morning than any pitol magazine you’ll ever own will be in its entire service life.

    A properly engineered spring that is not compressed or stretched past its limits in either direction should be able to spring away for a long, long, time.

  7. ben Says:

    I’m in with the “compression fatigue is a myth” or at least likely a myth. Steel isn’t known to change formation due to constant stress/strain. If the deformation is plastic, it’s plastic right away and the spring is changed immediately and for life. In this case, it doesn’t matter how long you leave the spring compressed, it’s jacked up from the beginning.

    If the deformation is plastic, then leaving the spring compressed won’t change the structure in the metal. It is maybe feasible that repeated heating/cooling cycles while compressed over a decade or two could maybe be the culprit, but I doubt it if they’re stored in an occupied dwelling as the range of temperatures isn’t very great.

    Fatigue is the only way to really wear out springs, or any metal, if the deformation is only elastic. On the other hand, the mag might get full of dust and other gunk after a long period of storage, and that might affect it’s performance.

  8. ben Says:

    Argh. First sentence of second paragraph should read “If the deformation is elastic…”

  9. Tam Says:


    Indeed, which is what makes the exceptions I’ve noted so puzzling. But who am I going to believe? The engineer? Or my lyin’ eyes looking at the dead spring in my hand, less than two-thirds as long as when new, that won’t reliably feed rounds anymore?

    The only thing I can think of is that it is possible to design a mag with so little margin of error that small variances in spring quality can have disastrous results in longevity.

  10. Jay G. Says:


    I started writing that before you posted and apologize for the blanket statement.

    Right after I hit “submit comment” and read your post, I cursed the gods of unfortunate comment submission… 🙂

  11. Jailer Says:

    Well having just replaced over 150 Glock magazine springs I can tell you they do compress when left loaded for a long period of time. Will they still work? Probably. Will I take a chance with a fellow employees life to find out? Nope.

    With magazine spring fatigue just as with anything else I think the quality of manufacture of the initial product has more of an impact than anything.

  12. Skip Says:

    Gotcher Wilsons right here, loaded with eight for five years or more, along with a bunch of CM’s and GI sevens.
    None have failed to feed. I empty them through the barrels once a week.

  13. Seerak Says:

    All these gun nuts, and not one metallurgist? Seems to me that one of them could put this issue away with a single comment.

    Regarding Tam’s examples, I wonder whether they might have used the wrong alloy of steel, or had a bad batch.

  14. Mr Evilwrench Says:

    Alloy matters. The amount of compression matters. The valve springs in your engine aren’t expected to range from 7″ to 1/2″. In the absence of great heat, moving the metal causes more fatigue than having it sit, but some alloys just don’t spring so much in the first place. Notice how it’s certain manufacturers, when others are ok. I’d bet the ones that fail would do so no matter what you did with them.

  15. Diomed Says:

    Metallurgists have commented on this elsewhere. They just confirm what’s been said here, a properly designed and manufactured spring will last more or less indefinitely. That means no overcompression or stretching.

    Personally, with the exception of junky mags and very old ones (I’ve got some Lee Enfield mags that are borderline, and one or two that have actually had spring failure) which necessarily bear the limitations of the time when they were made, I would expect the mag bodies to suffer fatal damage before the spring dies.

  16. DirtCrashr Says:

    We’ll try to get around to it as soon as the year changes – it’s a cool old magazine, too cool to fail. 😉

  17. Karl Says:

    A couple of years ago my brother asked me to take his Llama .38 super to the range to see if it even worked. He had never fired it. It looked older than dirt and looked like it had been fired a million times in it’s lifetime. The magazine had been loaded for 13 to 15 years. The gun had not been cleaned in 13 to 15 years. It was stored under his dresser and covered with dust and dirt. I did nothing but take it to the range with his 100 rounds of old ammo and shot it until I ran out of ammo. Not a single glitch, worked perfectly. I offered to buy it, my brother wouldn’t sell.

  18. Tam Says:


    Gotcher Wilsons right here, loaded with eight for five years or more, along with a bunch of CM’s and GI sevens.

    I don’t doubt it. Still ,the only way to find out if you’ve got a bad spring is to kill it, and the fact remains that I’ve seen bad springs in 47Ds. (Incidentally, due to follower length and other factors, CMCs do not have this problem, nor do GIs; neither compresses the spring as flat as the Wilson.)

    I’ve seen it. With customer guns and my own.

    Nothing like buying a Springfield Pro, inviting somebody to meet you at the range to shoot your new gigabuck auto, and have it malf on two mags with springs so broke-dick they wouldn’t feed.

    Mind you, I use Wilson 47Ds exclusively, but the only ones I’ve ever needed to replace the springs on were back when I kept them loaded with eight rounds. Haven’t had to since. Maybe my elephant dance is keeping the elephants away?

  19. Tam Says:


    Not a single glitch, worked perfectly.

    While I’m not surprised at the mag spring still being good, the fact that the Llama ran a hundred rounds without a malf would be surprising even if it were new. 😉

  20. Tim Says:

    As long as we’re picking nits, I’ll point out that this is not really an experiment. For it to be a true experiment, you would need to take a sample of magazines, randomly assign them to two groups. Load up one group with ammo, while storing the other group with ammo unloaded. Then wait 10 years, etc.

  21. Laughingdog Says:

    Tim, people already did experiments in metal fatigue years ago, and the results of those experiments are sufficient to state affirmatively that what Tam said is correct. Properly designed magazines will not be affected by leaving the magazine loaded.

    As long as the stress applied to the spring is not sufficient to cause plastic deformation, staying compressed will have no effect. One possible exception to this would be if the magazine went through very large temperature swings while stored, because that would effectively be a form of cycling the spring. But any swings that would jack up the spring would most likely screw up the ammo long before that anyway.

    Tam’s comment about the Glock mags was good to know though. I may have to download those a couple of rounds.

  22. PawPaw Says:

    Last summer I found a loaded AR mag that I had loaded when I came home from Desert Storm and had to escort a couple of racks of M16’s to our armory. That mag was loaded in 1991. In 2011 I fired it as part of my normal LEO qualification with the carbine. It ran fine after 20 years. The mag itself was a GI issue mag made by Okay Industries. It’s still in my carbine bag, loaded with new ammo.

  23. Seerak Says:

    Metallurgists have commented on this elsewhere.

    Oh yes. Been googling around. Never mind what I said, some debates just won’t die. Being familiar with the example of audiophiles, I should have known 😛

  24. J.S. Kidd Says:

    My father has a WW2-vintage Browning Hi-power with a spare magazine. He has kept both magazines fully loaded for the last 65+ years. Both still function smoothly and reliably.

    A friend has a Walter PP with a spare mag that she bought in the early 1980s. She has always kept both mags fully loaded and both still function fine.

    Another friend has a Ruger Standard from the late 1970s. Both mags have been kept loaded at all times and both still function fine. He also has a Beretta 92 from the mid-1980s with a total of four magazines, all kept loaded, all still fully functional.

    And lastly, a co-worker of mine bought a Para-Ordnance 14-45 in 1991. For the last 20 years it has been kept in Condition 1 (“cocked-and-locked”) with a fully loaded magazine and two fully loaded spares. Neither the magazine springs nor the pistol’s mainspring show any signs of deterioration.

    A spring failing due to compression would be a sign of inferior metallurgy and/or poor design (exceeding the elastic limit of the metal). Good quality springs in properly designed magazines should last for centuries of static storage.


  25. Henry Says:

    This sounds like a Mythbusters episode – measure the spring pressure of some magazines from various manufacturers.

    Load all, put into two piles (a control group, and a shooting group)

    Take the shooting group of mags, shoot them and shoot them again, repeat as much as possible, then measure all the magazines again at the end of the test. Measure the feed lips and all the other critical dimensions too. If there is anything to this controversy, you should be able to measure a difference one way or another. Save some loaded magazines for the revisit next year, and the year after that, etc.

    It seems to me that CMC could do this test with their mags compared to “Brand X”, and make a lot of money selling magazines, replacement springs, and followers.

    They could have a cache of magazines stored in a torture chamber in Death Valley or or Knob Creek, or somewhere, and bring one out every year to demonstrate that it still works, with many press releases and you-tube videos and free hot dogs.

    Yum! I love hot dogs!

  26. FormerFlyer Says:

    Seconding (thirding? fourthing?) Tam’s comments above: Picked up a Colt 1908 that had a full magazine that had reportedly been loaded when the pistol was given, new, to the owner in the early 1930’s. Owner passed, grandson sold the pistol to my father, and we shot it for the first time since it left the factory, with that ammo, in 1997. Ran perfectly.

    Found a Glock 17 magazine in 2010 that I had loaded up for my brother’s pistol in 1988. 17 rds of Winchester Silvertip. Ran perfectly.

    Tried an old after-market Browning P-35 magazine that I had function tested, then loaded up and stored for 6 months. Dead. Would not feed. Spring was compressed to about half the length of a factory new spring. Don’t know what length it was originally, as it was aftermarket. Same number of turns in the spring, but definitely different gauge wire (thicker than the factory one).

    Bought a “Blue Sky” Garand, “arsenal refinished” from Korean War surplus inventory in 1987’ish. Ran fine for 15 rounds, then the main spring (bolt return spring?) fractured in 6 pieces. Apparently nobody told the arsenal that refinished them that you shouldn’t parkerize the springs.

    Whether they take a “set” or wear from cycling depends on the quality of the original manufacturing process, the design of the spring, and what’s happened to it in the intervening years. Good springs shouldn’t take a set. Both “Good” and “shouldn’t” are not absolute, and are not always apparent to the user. YMMV.


Remember, I do this to entertain me, not you.

Uncle Pays the Bills

Find Local
Gun Shops & Shooting Ranges