Spring Fatigue Or Deformation From A Fully Loaded Magazine?


Many people wonder about this – whether or not the spring will eventually become deformed or fatigued in a fully loaded magazine – or if it’s best to keep your firearm’s magazine (magazines) unloaded for spring longevity – or if it doesn’t make any difference at all…

Here’s what I’ve learned:

IF your magazine is of reputable quality (e.g. from the firearm manufacturer or a source that you trust), this will presume that the SPRING inside the magazine will be of proper design specification for it’s intended purpose (to hold ‘X’ number of rounds of ammo) and will be of proper manufacture.

When a magazine’s internal spring is forcibly compressed (by inserting rounds of ammunition), it could in theory remain in this condition for countless years and will return to it’s original shape when the force is removed (expelled ammunition).

This is called “elastic deformation” – which is the action of the spring “deforming” while under force, but only temporarily, because it will return to it’s original shape when the force is removed. This deformation is temporary due to the specifications and design of the spring.

However the spring may become irreversibly and permanently deformed (called “plastic deformation”) after an increasingly higher number of elastic deformations (cycles).

Translation: The more times a spring is loaded and then released (over and over and over), the more likely that tiny fractures may develop within the metal of the spring. Depending on the metal material itself, and how close to the ‘elastic limit’ that the spring is repeatedly ‘deformed’, it may literally require thousands, millions, etc.. of elastic deformations before this might occur. This is called metal fatigue.

Metal fatigue will increasingly permanently deform the spring and eventually may fracture all together.

What I’ve learned:

IF you have a quality magazine (spring) that is designed for it’s intended use (“elastic deformation”) up to “X” number of rounds spring compression — the spring will always return to it’s original shape (and therefore no issues of ‘feeding’ rounds via the spring itself), no matter how long you leave the magazine fully loaded.

Having said that, if the spring becomes damaged – rusty, all bets are off.

In theory, the more you use a given magazine (spring), the more likely that spring fatigue will set in over time. However a well designed spring could last “forever” without any noticeable fatigue, given that it’s upper limit of elastic deformation should be well away (hopefully) from the designed force that the spring will ever experience.

Will loading one less round into the magazine extend the life of it’s spring while using it over and over again this way? I would say yes, IF that spring was designed such that it’s full compression is close to the limit of “elastic deformation”. I would also suppose that a magazine purchased from the firearm manufacturer would be of sufficient design to be able to fully load said magazine without having any issue whatsoever over time.

It comes down to quality and how these springs are made (their design and manufacture parameters). While manufacturers (in general) continue to cheapen their products to improve margins, it is unclear whether or not this is affecting certain firearms products and/or their accessories – including magazines and springs. Just buy ‘quality’ and be done with it.

…my 2 cents.


  1. BTW: In Nam it was recommended we put one less round in the magazine.

    1. That makes sense if these springs (or some of them) are manufactured close to their “elastic deformation limit” in it’s design – which could potentially lead to spring fatigue over many uses. I suppose the only way to know for sure would be to understand and examine the specifications of a given spring design for a given magazine – but I tend to think that the manufacturer might not reveal this…

      “When in doubt, leave one out” ?

    2. Kliph,

      One less round had to do with the fact that a fully loaded GI magazine had no give left in the spring so it could not be loaded on a closed bolt. So it became standard to load 19 in a 20 round mag and 28 in a 30 round mag. Current issued GI magazines are still that way. Magpul has built into there magazines this extra give of the spring so you can load a fully loaded magazine on a closed bolt.

      1. Well, it’s been a while(almost 50 years) but I thought it was about
        the spring. We could close the bolt with a full mag, if I recall.
        But it’s been a while since I slept with my rifle.

        1. Closing the bolt and charging it was not the problem. It was loading on a closed bolt. Have a full GImag would not allow enough give in the spring to allow the magazine to lock. Thus the download rules.

  2. I had one magazine spring actually break. No visible rust or damage, but I have no idea where that mag came from. It, and two others came with an old .303 British rifle I bought about 30 years ago. The other two that came with it are still going strong with no problems, and they stay loaded all the time.

  3. Have spares for mine , keep two loaded at a time , change them out every six months , have not had any trouble as of yet . I have always practiced what Kliph said , just makes sense to me . Be prepared and ready . Keep your powder dry .

  4. That’s funny. I just looked at my magazines this morning, thinking it was time to rotate. I keep 1 (fully) loaded and rotate to a different magazine every 6 months or so.

  5. Never had a fully loaded mag spring(rifle or pistol) go south on me yet. Of course, the “Murphy Family” has yet to visit those mags as well…

  6. I’ve never had a magazine spring fail. When I think about it, I’ve never spoken to anyone who has. Magazine rebuild kits are cheap. At present I have eighteen magazines for my AR. Half of which have never been used. Three are still in the original plastic bags. PMAGs are better than USGI, ducking, IMHO.

    Yes, the rifle that fell out of the boat on a hunting trip. A tragic loss.

    I keep the other nine loaded with twenty rounds each. I figure that 180 rounds will give me sufficient time to refill. If not, my prepping concerns are over.

    Don’t forget ammo cans and stripper clips.

  7. Professional metallurgical engineer: yes, correct. Load em and leave em.

  8. interesting…..

    “A plan by police in Buffalo, N.Y., to begin confiscating the firearms of legal gun owners within days of their deaths is drawing fire from Second Amendment advocates.

    The plan is legal under a longstanding, but rarely enforced state law, but gun rights advocates say, with apologies to onetime NRA spokesman Charlton Heston, it is tantamount to prying firearms – some of which may have substantial monetary or sentimental value – from the cold, dead hands of law-abiding citizens.

    “They’re quick to say they’re going to take the guns,” said Tom King, president of the New York State Rifle & Pistol Association. “But they don’t tell you the law doesn’t apply to long guns, or that these families can sell [their loved one’s] pistol or apply to keep it.”

  9. Not too long ago, I fished out an old 1911A1 that I bought back in in the 70’s. The mags were loaded for over 30 years. During a trip to the range, all worked “as advertised” though the mags were showing some signs of rust so I replace them. No sense pressing my luck.

  10. Decades ago when cops were transitioning from revolvers to autoloaders, we started to observe some trends within the gun industry: #1 some high capacity magazines for some pistols can be very expensive (Beretta, H&K, SigSaur, S&W) When a cop is carrying normally 3 magazines and each new mag costs around $80 per mag, Do the math…costs add up fast. #2 During peacetime, the biggest threat to gun mags is tactical training drills where partially ejected magazines land on concrete and may/may not get stepped on. (quick way to ruin a gun magazine). #3. If your pistol jams, try switching out the magazine.
    Those cops that are making the car stops, responding to 4-15 domestics and going through doorways are at the lower end of the pay scale. (you do not hear about captains working the graveyard shift pulling over cars). Cost of replacement parts and aggressive marketing to police agencies is why Glocks became the preferred choice among LEOs within this country over the past 30 years. Last note: This site and others have been promoting GunMag Warehouse as a great online source of new magazines for your home defense or carry firearm(s). I have called them for business many times since I discovered MSB over a decade ago.

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