If I keep my M&P 9mm mags loaded will it damage the magazines eventually? I haven't not had any FTF in a couple years now, but am a bit concerned I may be wearing down the springs.

If it does cause eventual damage, how many rounds can I keep in the mags of a full size or a compact and still have long term dependability?

Keeping mags loaded will not damage them. Mag springs are cheap and can easily be replaced if you do end up with some kind of feed issue. Mag spring issues are more gremlin related rather then being caused by keeping mags loaded.

Stay safe!

Ed

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DAV / NRA Endowment Member

OK to keep loaded, it's repeated loading and unloading that wears springs out.

The officer that taught my gun class just recommended not doing the full capacity +1. He said it would help to do a full load in the mag and then if you want one in the chamber rack it but don't add one back in the mag. His reasoning was more for the base of the mag, which he said he had seen a couple fail from the pressure being in the mag for a long period of time. It made since to me and 15 rounds instead of 16 isn't that big of a deal to me.

This should not be an issue for any properly designed and well constructed magazine. Your call. Mine are used full capacity plus one.

Modern pistols like the M&P are primarily designed for military/LE use. Neither of which has the time to worry about magazines or go through rituals of down loading or rotating. Quality magazines and their springs are designed to remain loaded to full capacity over a long period of time with reliable functioning. Topping off the magazine after chambering a round is proper and is included in the magazine design. Bill

Sarge got it right. Google Hooke's law of elasticity. Assuming proper raw material choice and proper manufacturing process, and as long as it has not exceeded its strain and elastic or compressive limit, the spring will continue to function as designed in its application theoretically forever.

Working within these limits, basically the only destructive force would be the atmosphere eroding the material. Raw material contaminants and abuse outside the functional intent can reduce the life of a spring also.

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Marty 4513TSW 13-1 642 60-10

I usually keep mine either loaded or unloaded....

I was once given a loaded 25 auto magazine (probably a baby Browning) continuously loaded for over 50 years since WWII and I was recently given a Browning Hi-Power magazine loaded about 30 years ago and forgotten. Upon removing the rounds, both magazines functioned just fine and I detected no weakening of the springs.

However, I generally don't top off my mags if a fully loaded magazine cannot be easily inserted under a closed slide.

I've fired both M1911 and P'08 magazines last loaded 50 years prior. No problems. Fired M16 magazines loaded 30 years ago. (Amazing the stuff in old foot lockers!)

Full magazines seem to load fine in closed slide/bolt weapons for me. Only "advantage" in downloaded magazines is less ammo.

-- Chuck

Follow the manufacturer's recommendation. They know better than us.

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VIVERE MILITARE EST

What are S&W recommendations on this?

Reviving this thread since it basically asked the question I came here to ask and didn't want to create another thread.

I just bought an M&P9 CORE and have 5 total mags ... I keep them full (I'm in CA. so full is 10 rounds).

I was wondering if this was okay to do at all times on these springs or if it causes issue over time?

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M&P9 Shield, M&P9 CORE, S&W.38

A properly made spring in a static state (full or empty) doesn't cause spring fatigue. Its the work a spring does over time that causes 'wear'.

New springs generally take a set after a short period of time, which is normal so comparing a used but good spring to a brand new one isn't a proper comparison. The normal recommendation is to fully load a new mag a few days before you use it for the first time for proper function.

I know this is the M&P forum but the same question gets asked regarding whether they should keep the hammer cocked on a 1911 or not all the time and it's perfectly fine to keep it cocked.

i keep mine loaded at all times no problem its a spring let it do its job

All mags in all my guns are fully loaded and there is always one in the chamber.

This most excellent post should be a sticky at the very top of each gun forum in the world.

Very few firearm topics generate so much myth and misunderstanding as springs do.

FWIW the mags for my Glock 23 have been loaded long before I retired in '97 and continue to function absent any problems.

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Old Cop
LEO (Ret.)

Loading mags to one less than capacity for a self defense gun, especially for those spare mags intended to be used for reloads, can be very helpful in accomplishing a tactical reload (some rounds fired, slide in battery, round in chamber, but you've found cover and want to "freshen up). A full mag is much more difficult to seat properly.

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Wisdom comes thru fear . . .

Fully loaded all the time +1. I've only encountered a few guns that needed the magazine hammered in when fully loaded. One was a G30SF weather it was the 9 or 10 round magazine. I kid you not when I say that I had to hold the slide like a handle and hammer the butt end of the gun with the fully loaded magazine to get it to seat. Once seated, it was like dragging two files across each other when trying to chamber the top round. I even cut off coils in the mag springs and it was still the same. Weather someone's G30SF also does that or not, mine did and became a terrible firearm design in my mind. It was that or Glock was trying to fool me into thinking those were actually 9 and 10rd magazines. Loading them was a major pain as well. I left them loaded minus a round for a month and I still had to use all my strength WITH a magazine loader to get the last round in.BTW,I never hammered it with a round already in the chamber. Long story short, I got rid of that abomination ASAP.

Second one was a SD9VE. It wasn't nearly as hard to seat as the G30SF, but it was enough that I left it at 15+1rds. It's no big deal since it's the same size and capacity as a G19 at that point. The 16th round was easy to load, but the mag wasn't easy to load on a closed slide.

That's all I can think of off the top of my head. Besides those two, the fully loaded mags on my semi-auto handguns are easy to insert and kept that way until I shoot it. The repetition of compressing and decompressing the spring causes fatigue, not keeping them loaded.

"Eventually"? Yes. Whether that should be a concern to you is debatable.

The fact that a magazine spring will "break in" and take a set isn't exactly a good thing... technically. That means the spring steel has undergone some plastic deformation and lost some of its free length. Good thing is, this is not a self-perpetuating problem. As the spring free length is reduced, so is the spring rate, albeit slightly. This reduces total force the spring will exert when compressed, accordingly so is the stress it sustains. At some point, there will be an equilibrium point where the stress is less than what it takes to induce further plastic deformation. That's the spring "taking a set".

A good magazine design balances between competing goals:

1. Minimizing weight and bulk
2. Reducing stress/wear on other parts of magazine (lips, for example)
3. Maximizing service life

If a magazine spring takes a set, it could be that the engineer intended for the above mentioned equilibrium point to be reached quickly. You can, of course design a magazine spring that have so much capacity that it will never take a set, but then you add weight and bulk... or mfg cost using higher-performance material. Good design means a magazine spring is just long/strong enough to perform well in its expected service life.

So... should you worry about all this? Depends on how anal you are, I suppose. Magazine springs rarely fail catastrophically, so you can always change them out when you start noticing performance problems. More than likely, a quality magazine in civilian use will outlast you and your children combined.

Personally, I use them to the full capacity... in general. On lower capacity mags like my Shield 40 and Bodyguard, which only holds 6 or 7rd, by golly I'm using every last rd of capacity I paid for. OTOH, downloading a 20rd mag to 19 probably isn't gonna make a whole lot of difference tactically. Not a bad idea especially if that 20th round is a bear to push in.

BTW, I doubt anybody can load/unload a magazine fast enough - or often enough - to frequency-fatigue a typical magazine spring. To do that, you'll have to exercise the spring at high frequency and duration, which a normal working magazine will never experience.


Suffice it to say, if I have an antique German Luger .45, I probably would not load the magazine full and leave it sitting.

This question comes up so often that I decided to email MAGPUL and get a expert answer. Below is my email to them and their reply.

to magpul
Could you please help clear up the issue of magazine spring fatigue. Should you periodically unload and "relax" the magazine spring? Will this help to increase the life or does it do more harm than good.

Thank you


Tricia Parrish <[email protected]>
Jan 10

to me
Jerry,

Thank you for your inquiry. The factor that truly wears out quality springs is compression cycles, not constant compression. However, we use a high-quality stainless steel springs in our PMAGs and if one ever does happen to wear out any USGI spec spring can be swapped out for the factory one.

Regarding the question of how long, we’ve had magazines fully loaded for over four years now with no Impact/Dust Cover on and have experienced no feed lip or spring issues. With the cover installed storage life is considered indefinite. There have also been PMAGS reportedly tested to hundreds-of-thousands of rounds (military vetting), and we know positively of ones that have gone tens-of-thousands, so usable life is quite excellent too.


Magpul
_____________________________________
TRICIA PARRISH SALES & CUSTOMER SERVICE

MAGPUL INDUSTRIES CORP.
[P] 303.828.3460 x141 [F] 303.828.3469
[email protected]
magpul.com | magpuldynamics.com

I have a gun I've never had more than one mag for, and it's basically been kept loaded for 20 years when not in use. Works fine, and it's still hard to get the 13th round in.

S&W recommends changing magazine, recoil and trigger springs on the M&P series in duty use (continuously loaded) every 5 years. Our armorer isn't in yet, so I can't ask about extractor springs. Probably that too. High round count can reduce the intervals, which I think are based on a 5000 round count.

My personal M&P9 was purchased in 2006 (first production run) and I haven't changed anything yet. No issues and, yes, it's been continuously loaded since then. Except when dispensing the several thousand rounds it's fired.

GREAT Info in here guys ... thanks so much for all the feedback.

So really it seems to be a non issue to keep mags loaded at all times from what I gather.

Good to know, Thanks again.

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M&P9 Shield, M&P9 CORE, S&W.38

I found this article years ago:

Magazine spring madness: 'creep' to your 'elastic limit' to un-earth the urban legend of 'spring-set'

by John S. Layman

The shooting sports are full of some of the most knowledgeable and capable people you'll meet anywhere. I've been impressed consistently with the abilities of those I meet at the range to diagnose and fix a gun problem with as little as some spray lube and a cotton swab. However, sometimes a myth will creep into the folklore.
The magazine spring myth has been around for many years and is growing in popularity. It goes something like this: "You should unload your magazines when they're not in use or the spring will weaken causing failures to feed." This has gone as far as shooting competitors actually unloading their magazines between stages to extend the life of their springs. A variant of this myth is: "You should never load a magazine to capacity and should always leave it one round short." What if you need that round some day?
Recently, I read an article in a gun magazine suggesting you rotate your magazines so the ones not in use can "recover and rest." The same author uses the phrase "spring-set" to describe weakness of a spring because it was compressed for a long time. Hogwash. There's nothing further from the truth. Springs don't care how long they're compressed and don't require rest, recreation or even a vacation from time to time.
Shameful Spring Benders
To put this one to rest, you have to understand creep. Creep is the slow flow of a non-ferric metal like copper, brass and lead under force. At temperatures outside of a furnace, steel doesn't have any appreciable creep. Under most conditions, steel flexes and then returns to its original shape. When pushed past its elastic limit, steel will bend and not return to its original shape. All designers of well-made magazines make sure the spring never approaches the elastic limit when the magazine is fully loaded. Honest. This means the spring will not weaken when the magazine is fully loaded -- not even over an extended time. Like 50 years. American Handgunner recently ran a story about a magazine full of .45 ACP that had been sitting since WWII and it ran just fine on the first try. So there you go.
Now that the light of truth is leaking out, lets talk about what is causing failures to feed. The only way to weaken a magazine spring is to flex it past its normal range (elastic limit). If this is happening, somebody is trying to overload a magazine or has "adjusted" it by bending the spring. Both of these could cause feed failures. Shame on you if you're a spring bender.
Carlton Nether, Customer Service for Beretta USA, tells us keeping a pistol magazine loaded for an extended period doesn't cause magazine spring failure, however, failures to feed can result. He says, "The ammo will 'roll' in the magazine. If the mags are kept loaded and moved around a lot -- say on a cop's belt -- the rolling action can, over time, cause creases in the cases. These creases can cause malfunctions. Also the top bullet will roll against the magazine lips and creasing can occur there as well. Just check old ammo that's been bouncing around in a magazine for a long time.
We tell police officers if they keep loaded magazines, take a few seconds to "cycle" the ammo. Periodically unload the mag and reload it in a different sequence. This movement will allow the bullets to be in different parts of the magazine and help eliminate creasing.
At STI, Dave Skinner, President and CEO says, "Personally, I rotate my 'under the bed' and 'under the seat' mags about every six months. I always empty them the 'fun' way and have never had a failure." Given what we
learned above, this sounds like a good idea. Smith and Wesson customer service also says magazines can stay loaded indefinitely without hurting the spring.
As we add force onto a spring, it will displace the same amount for each amount of force we add. This is true until the spring passes a certain point called the elastic limit. Robert Hooke discovered this theory back in 1660. Hooke's Law states: "If the applied forces on a body are not too large, the deformations resulting are directly proportional to the forces producing them." Which means, in actual human being language, if we load a spring past its elastic limit, it permanently deforms. It still provides a force against the load but the force is no longer proportional. If this happens, when we unload the spring (such as when we empty a magazine that has been over-loaded) the spring never returns to a state where it can provide the same load for the same amount of displacement.
Trust Us
When a magazine manufacturer designs a spring, they plan for a preload. The spring is already compressed some in the magazine. On the curve below, this would be Point A. The spring compression would be designed to be below the Elastic Limit. When fully compressed, the spring would be at Point B. If the spring is ever compressed past the elastic limit, say to Point C, it won't ever behave the same. Like a recalcitrant lazy Uncle, it will have a lower spring force for each amount of displacement. On the drawing, the spring would now cycle between points D and E. This means that -- particularly with the last bullet or two -- the force pushing the bullet up would be less and lo-and-behold, a mis-feed might occur.
When somebody stretches your spring to "fix" your magazine, they are trying to get you back on the original curve. They may get pretty close, however, it's unlikely the spring will ever perform to its original design. The elastic limit is now shifted lower and your magazine spring may fail to perform fairly quickly.
Having said all this, if you have a magazine that isn't feeding right, what should you do? First, disassemble the magazine and clean it thoroughly. Then try it with new, factory ammunition in a freshly cleaned gun. This takes away some of the possible causes. If you are still having feed problems, send it back. Even the low cost, after-market magazine manufacturers will fix the problem at no cost to you other than shipping. If it's a magazine from the gun's manufacturer, let them troubleshoot and repair the problem. Otherwise, toss the mag. It's not worth risking your life to save a few bucks. And that's the truth.
RELATED ARTICLE: Definitions
Creep: The flow or plastic deformation of metals held for long periods of time at stresses lower than the normal yield strength.
Elastic Limit: The maximum stress that material will stand before permanent deformation occurs.
Yield Strength: The stress at which the metal changes from elastic to plastic in behavior, i.e., takes a permanent set.
Permanent Set: Non-elastic or plastic, deformation of metal under stress, after passing the elastic limit.
Magazine Recommendations
* Clean your magazines when they get gritty. Apply oil then remove all excess. Oil attracts dirt that may cause malfunction.
* If you find rust on the spring, this is culprit. Rust changes the thickness of the metal and reduces the force applied to the follower. Cleaning off the rust may help. For a gun you depend on, replace the spring. All the major brands and most of the smaller ones have replacement mag springs available or try Wolff Springs.
* If you keep a magazine loaded for long periods, rotate the rounds every few months. If you carry a pistol on the job or in your car, cycle the ammo frequently. These actions prevent creases from forming which may cause a misfeed.
* If you experience feed problems, first clean your magazines and weapon. Fire a couple magazines of new factory ammo to see if this resolves the problem. If not send the magazine back to the manufacturer -- or toss it.

I have proven, though some don't believe it, that a spring will lose length when kept compressed for a long time. However, that's not really the question, is it? The real question is, "Will my magazine/gun fail to work if I leave its springs compressed?"

To that end, the answer is a resounding no. Yes, leaving them compressed will affect them. No, that affect is not significant to the operation of the gun.

So, leave your hammers/strikers cocked and your mags loaded. They will work when you need them.

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Freedom isn't free.

Is it OK to keep my M&P mags loaded?

Yes. They're pretty well useless if they're empty...

Yep thats what I was thinkin ... but I just wanted to make having all 5 in my range bag loaded at all times was okay and didn't lessen the life of the spring etc. or maybe cause issues earlier then expected.

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M&P9 Shield, M&P9 CORE, S&W.38

If some of you are so worried about wearing out your mag springs, why not change them out every few years? If that makes you sleep better at night.

I find it funny that folks blow through boxes after boxes of ammo at the range, yet fuss over longevity issue on $3 springs.

Buying brand new springs for ALL my magazines would cost less than an oil change for ONE of my cars.

Sorry to be blunt, but this is borderline hypochondriac.

Cheap and poor design, poor materials magazines suffer from feed lip deformation more than spring fatigue. Good mags hold up better. Dropping mags with ammo in them is causing lip deformation even in good mags when they hit lip down.

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A republic if you can keep it

I'll be sure to contact you to see if you can spare a few bucks for me to replace my 5 springs ... That's if ONE of your Many cars (aren't you cool) doesn't need an oil change that month.

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M&P9 Shield, M&P9 CORE, S&W.38

All I was saying is to keep things in perspective. A $3 spring is less than what a lot of folks spend on a frappuccino every morning. And just about every average household in America has more than 1 car. Nothing special here.

There are cheap ways to mitigate that magazine longevity concern. That's all.

An even cheaper way... don't worry about it.

Most quality 1911 magazines will go indefinitely, it seems.

My double stack 40 S&W mags made it just shy of ten years. They didn't fail completely, but would often leave the last round or not activate the slide stop. A few Wolff springs will have them going for another decade or more, I'm sure.

Springs will not lose their tensile properties if you apply a steady load for any length of time. How often do you have to replace the valve springs in your engine or the suspension springs in your car - they work a lot harder than any of the springs in your gun. It is a naive myth that if you keep springs compressed for a long time they will lose their tension.

Mag springs are more than $3 though. 1911 mag springs are about $8 a piece.

Even so, your point is well taken. If a guy were to refresh three mags a year it's still cheap insurance. Not necessary, but not expensive either.

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Freedom isn't free.

You can keep all your magazines loaded forever.

In well made magazines, storing them loaded for many years does no harm.

+1 for "administrative loading". I keep all my mags loaded to full capacity.

I based it on MidwayUSA. But you're right, a lot of other places sell it at $7-8, including wolfsprings.

Personally, I wouldn't bother unless there were obvious problems.

These days, a lot of car mfrs list spark plug replacement at 100k miles, but folks who still insist on changing them out way sooner, even though there are no perceivable problems. Nothing wrong if that makes you sleep better at night.

Simple answer is no. Metal fatigues when it moves between the states of uncompressed and then compressed in the case of mags. Keep them loaded or in a compressed state is no different then in an uncompressed state. They wear out by using them over and over again.

Metal fatigue is not the issue. Nobody can cycle those mag spring fast enough, close to its natural frequency and for long enough duration, for that to be a problem.

Mag springs do lose a bit of their "shape memory" in normal operation. To see this, you'll have to take the spring out of the magazine and measure the "free length". Do that when the mag is brand new unused. Then repeat some time later after constant usage. More than likely, you will see a slight - but noticeable - difference in free length. Whether this difference will affect operation of the magazine is an entirely different issue.

Spring steel, when formed into the shape of mag spring in the mfg process, will carry some residual stress. Normal operation of the mag in use will relief some of that stress. This is another reason that folks notice a mag spring taking a "set" after some usage. It it normal and do not typically affect operation.

That is the best explanation of this topic that I've seen.

People notice that springs exhibit a reduced length after use and assume that they are "weaker" which is not the case during the design useful lifetime of the spring.