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I have done extensive research on the past and borrowed my wife's knowledge (she's an engineer) and her co-workers along with the knowledge of several professional shooters to come up with this data.

Several people carry there spare magazines -1 or store the magazines that they are not using at the time unloaded. They do this because they believe that this relieves some of the stress that is put on the magazine spring by not having it fully compressed. Stress on magazine springs is caused by constant compression/decompression I.E. actually using the magazine for range time or constantly loading/unloading.

This actually makes perfect sense if you think about it for a second. Take a normal spring of any sort and set it under an object such as a book to where it is left fully compressed. You could leave it in that manner for years and when you finally removed the book to where it is only decompressed once, there would virtually no difference in the compression rate than the first day that you had put it under the book. Now if you were to take the same spring and compress/decompress it constantly as if you were playing an accordion, it would last a fraction of the time.

The springs that I let the engineers use were single stack Sig, Kimber 1911, Chip 1911, Glock 36, and Springfield 1911, double stacked Springfield Xd45, Glock 30, Glock 21, Vietnam Era GI mag, Promag Ar 15, Magpul Gen 1&2 Ar15 30 and 20 round mags.

Something to take into consideration, all of the magazines have been manufactured within the last 50 years. If you have a early model 1911 with original parts or some other antique type firearm than you may want to do your own research of replace the OEM parts with more modern springs that have been manufactured more recently. The way that metal has been shaped and formed and what it is bonded with to make more textile has evolved over the last 100 years. So it may have been the case in the early years of magazine fed firearms to have to take precautions to make the spring last, it really doesn't apply to modern firearms. Also, where you store your mags and ammo plays a big role. If you bury them on the beach next to saltwater then naturally there will be some corrosion (or carry it on your persons with salty sweat daily) compared to storing them in a safe with a humidifier. Ammunition and the magazine springs are metal which is still susceptible to natural elements. If you are ever in doubt switch them out. Most individuals with any mechanical inclination can change a magazine spring especially with the invention of YouTube being used as an aid.

Even with these findings it would be smart to know that everything has an expiration date. If you rotate ammo, use your mags at the range, or any other function that will make the spring compress/decompress you are putting wear and tear on the spring, but if you are like me and have 30 Pmags laying around loaded to capacity for the family to grab for whatever reason, you don't really have to worry about a FTF or other malfunction due to a bad spring unless there was already a flaw in the spring/mag (which is always a possibility even with modern manufacturing and QA).

Now you know and knowing is half the battle

bravomikefoxtrot wrote: Now you know and knowing is half the battle

What if I already knew?

SQLGeek wrote:

bravomikefoxtrot wrote: Now you know and knowing is half the battle

What if I already knew?

I just wanted to use my GI Joe reference. The 80's version, I'm not to sure on this new stuff

I would have to agree with the OP:
I walked around for a year straight carrying my 9mm magazine fully-loaded.
I have done the same with my .40cal magazine with no ill-effects noted.

Take a spring (any commercial compression type), measure it's length, at room temperature collapse it right up to it's Elastic Limit or Yield Point in a fixture and with it still compressed (near it's yield point at room temperature) cycle it through extremes of temperature (0F to 100F) 1000 times (a couple years worth) then decompress the spring and measure it again. Guess what happens.

This coming from another engineer. Me.

In all honesty, it boils down to the spring AND magazine design. If the magazine is designed where the spring compresses near it's elastic limit (fully loaded) and if the material chosen for the spring does not accommodate the yield point variance through the temperature range you will have deformation of the spring. Straight out of spring theory or strength of materials class 101.

Anyways, that's the straight physics of it. You can work the living caca out of a spring as long as it was designed properly into a system that keeps it well away from it's yield point throughout it's temperature range. If you don't trust me on this go outside and look up underneath your car/truck and tell me what you see. But compress a spring even once it up to it's yield point at a given temperature and then raise it's temperature thereby moving it's yield point and you will have a deformed spring. Some of our older makes of autos actually had this issue.

Now, do modern magazine designs take all this into account? I don't know or can speak for all of them. I do know that I have worn out AR mags that refuse to feed the last few rounds. As for my daily carry Glock mags I haven't seen any degradation over several years of daily use. But I will keep my eye on them.

esxmarkc wrote:Take a spring (any commercial compression type), measure it's length, at room temperature collapse it right up to it's Elastic Limit or Yield Point in a fixture and with it still compressed (near it's yield point at room temperature) cycle it through extremes of temperature (0F to 100F) 1000 times (a couple years worth) then decompress the spring and measure it again. Guess what happens.

This coming from another engineer. Me.

In all honesty, it boils down to the spring AND magazine design. If the magazine is designed where the spring compresses near it's elastic limit (fully loaded) and if the material chosen for the spring does not accommodate the yield point variance through the temperature range you will have deformation of the spring. Straight out of spring theory or strength of materials class 101.

Anyways, that's the straight physics of it. You can work the living caca out of a spring as long as it was designed properly into a system that keeps it well away from it's yield point throughout it's temperature range. If you don't trust me on this go outside and look up underneath your car/truck and tell me what you see. But compress a spring even once it up to it's yield point at a given temperature and then raise it's temperature thereby moving it's yield point and you will have a deformed spring. Some of our older makes of autos actually had this issue.

Now, do modern magazine designs take all this into account? I don't know or can speak for all of them. I do know that I have worn out AR mags that refuse to feed the last few rounds. As for my daily carry Glock mags I haven't seen any degradation over several years of daily use. But I will keep my eye on them.

Thank you for being more technical. I was about to warn the wife that she probably had some explaining to do just as soon as the questions started flying.

Springs are cheap life is expensive, change them occasionally.

esxmarkc wrote:Take a spring (any commercial compression type), measure it's length, at room temperature collapse it right up to it's Elastic Limit or Yield Point in a fixture and with it still compressed (near it's yield point at room temperature) cycle it through extremes of temperature (0F to 100F) 1000 times (a couple years worth) then decompress the spring and measure it again. Guess what happens.

This coming from another engineer. Me.

In all honesty, it boils down to the spring AND magazine design. If the magazine is designed where the spring compresses near it's elastic limit (fully loaded) and if the material chosen for the spring does not accommodate the yield point variance through the temperature range you will have deformation of the spring. Straight out of spring theory or strength of materials class 101.

Anyways, that's the straight physics of it. You can work the living caca out of a spring as long as it was designed properly into a system that keeps it well away from it's yield point throughout it's temperature range. If you don't trust me on this go outside and look up underneath your car/truck and tell me what you see. But compress a spring even once it up to it's yield point at a given temperature and then raise it's temperature thereby moving it's yield point and you will have a deformed spring. Some of our older makes of autos actually had this issue.

Now, do modern magazine designs take all this into account? I don't know or can speak for all of them. I do know that I have worn out AR mags that refuse to feed the last few rounds. As for my daily carry Glock mags I haven't seen any degradation over several years of daily use. But I will keep my eye on them.

This.

In my line of work we design springs to operate in a range up to 2/3 of the elastic limit. The other third is a safety factor. We can abuse the safety factor in some situations if we can show that the situation is temporary so long as we don't exceed the yield strength or the elastic limit. AND we can exceed the elastic limit in some cases (which DOES cause deformation) if we know exactly how many cycles and exactly how much stress. In these cases we have data on how many cycles we can abuse the spring, have some relaxation or deformation (acceptable and measurable), so long as we do not reach the Ultimate strength (which is the theoretical point where the spring will break).

The problem for magazine springs is that you, the owner of the magazine, has no idea if they are built to last forever or built to live for 5000 cycles. Practically speaking however, it is the cycling of the spring that causes failure more than a single compression (which is only one cycle). So, if you left it compressed all the time and rarely used it, the number of cycles is low and you would not likely see measurable change in the spring rate or neutral length.

AndyC wrote:Not to sound like a know-all, but I'm honestly surprised folks don't know this already. When exactly did it (erroneously )become "common sense" that springs wear out by staying in a compressed state in a magazine?

I couldn't tell you how many times I heard or read someone say " I carry one less round to save the spring" or "You keep your magazines loaded when you are not using them? That is going to ruin your spring."

You can actually find several videos on YouTube where this is being debated as well as most forums in some point in time. It's not as bad as the loaded/empty carry chamber debate but it is still brought up quite often.

bravomikefoxtrot wrote:

AndyC wrote:Not to sound like a know-all, but I'm honestly surprised folks don't know this already. When exactly did it (erroneously )become "common sense" that springs wear out by staying in a compressed state in a magazine?

I couldn't tell you how many times I heard or read someone say " I carry one less round to save the spring" or "You keep your magazines loaded when you are not using them? That is going to ruin your spring."

You can actually find several videos on YouTube where this is being debated as well as most forums in some point in time. It's not as bad as the loaded/empty carry chamber debate but it is still brought up quite often.

Enough said. I take most YouTube self-proclaimed experts opinions with a whole box of salt. Unless I am very confident in their background and know of which they speak I won't waste my time watching them.

As for the spring issue it is well known among the real experts that they don't weaken from being compressed over long periods of time.

Good to know. I really didnt know. I keep my 2 Glock spares loaded in a double belt pouch.

AndyC wrote:Not to sound like a know-all, but I'm honestly surprised folks don't know this already. When exactly did it (erroneously )become "common sense" that springs wear out by staying in a compressed state in a magazine?

It is a myth repeated on gun forums everywhere. It has been discussed here before. Here are a few

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I heard the myth 40 years ago in the Marine Corps. Old myths die hard, even in the face of facts.