How long can you keep magazine springs under tension?

[Walt Sherrill]

If you don't know why I think otherwise, you didn't read this thread either...the entire discussion is about mag springs *at room temperature*

Actually the entire discussion has been about mag and recoil springs with scant attention paid to temperature. It's not been an important point of focus. The phrase "at room temperature" was seldom mentioned and has NEVER been a key part of any of the comments I've made in this discussion. (I don't think I've ever mentioned it...) I can understand how a recoil spring COULD get pretty warm, with use, but not so warm as to affect the temper/strength of the metal. A gun THAT hot is not a gun I want to hold in my hand. I did NOT consider it a point of discussion.

I apparently misunderstood an important point about spring compression, and you set me straight. You said, in effect, that depressing a spring by physical displacement (using light plastic round replicas) will have the same effect on the spring as using heavier or actual rounds, as long as the springs are compressed to the same degree. If that happens -- i.e., the compression is the same -- the effect is the same.

Except for that misunderstanding (ignorance, really) on my part, the discussion has been focused on the effect of compression (or, arguably, OVER-compression) when the springs are near (or have exceeded) their elastic limit.

With coil springs, I would assume that "elastic limit" should really be considered "elastic limits," as the work is spread over many different places in the spring material. And, because MOST mag springs aren't pure coils, but hybrids, with long flat stretches of material connected to coil arcs and smaller flat stretches. It seems that these springs might act a bit like flat springs AND coil springs, and maybe with some torsion bar-like action thrown in at the corners. Recoilo springs are more typical coil springs.

Given all of that, I would expect degradation to be occur around the various corners in a mag spring, but not occur uniformly or simultaneously throughout the material. It could be a very slow process, and not even noticeable at first. With a recoil spring I might expect to see degradation to occur where compression first occurs... But, maybe I have all of that wrong, too. It won't be the first time I've had it all wrong. I've learned a lot from these discussions, and it seems worth the effort.

 

[danez71]

No kidding? "Time affects creep too"...????????

You do realize that creep *is by definition* time dependent deformation in materials, right?

Please be specific (as I was) as to what is contradicted? What is stated in any of those articles that contradicts the very simple and concise point that:

*creep in steels is not significant at the temperatures where ammunition magazines operate*

You can easily falsify the above statement by either:

1) showing that mag springs get up to 700F in service

or

2) showing that creep in steels is significant at much lower temperatures

Be specific...?

The picture/graph in your 2nd link has "time" and "strain" on the horizontal and vertical lines. Note: temperature in NOT part of the graph because the graph represents what happens with creep at "operating temp".

Eventually, if you compress a spring long enough, the molecules will start to realign and a spring will find its new equilibrium point. That might take 1000 yrs. Or it could take a few days.

However, other things such as temp, material, and how far it's compressed into its elastic range Influence how much Time it will take.

If you don't grasp that, you won't grasp anything else on the topic.

For giggles... what Temps do you think the recoil spring and mag spring see? What are you basing your info on?

I see you're now using qualifying words like "significant" and "properly designed" as a way to give yourself wiggle room.

What you also don't know is if the mfg decided that a spring is a consumable item and crammed more rounds into a smaller mag and thus compressing the spring deeper into its elestic range and shortening its life.

So, please tell us, how much creep, fatigue etc etc does it take to be "significant" enough to have an affect on performance of a mag spring for a glock... or a S&W... or Taurus?

As soon as you can define that, then you can start talking absolutes.

 

[Jlr2267]

Actually the entire discussion has been about mag and recoil springs with scant attention paid to temperature. It's not been an important point of focus.

The phrase "at room temperature" was seldom mentioned and has NEVER been a key part of any of the comments I've made in this discussion. (I don't think I've ever mentioned it...) I can understand how a recoil spring COULD get pretty warm, with use, but not so warm as to affect the temper/strength of the metal. A gun THAT hot is not a gun I want to hold in my hand.

I apparently misunderstood an important point about spring compression, and you set me straight. You said, in effect, that depressing a spring by physical displacement (using light plastic round replicas) will have the same effect on the spring as using heavier or actual rounds, as long as the springs are compressed to the same degree. If that happens -- i.e., the compression is the same -- the effect is the same.

Except for that misunderstanding (ignorance, really) on my part, the discussion has been focused on the effect of compression (or, arguably, OVER-compression) when the springs are near (or have exceeded) their elastic limit.

With coil springs, I would assume that "elastic limit" should really be considered "elastic limits," as the work is spread over many different places in the spring material. And, because MOST mag springs aren't pure coils, but hybrids, with long flat stretches of material connected to coil arcs and smaller flat stretches. It seems that these springs might act a bit like flat springs AND coil springs, and maybe with some torsion bar-like action thrown in at the corners. Recoiil springs are more truly PURE coil springs.

Given all of that, I would expect degradation to be occur around the various corners in a mag spring, but not occur uniformly or simultaneously throughout the material. It could be a very slow process, and not even noticeable at first. But, maybe I have all of that wrong, too. It won't be the first time I've had it all wrong. I've learned a lot from these discussions, and it seems worth the effort.

My 2nd post mentioned "temperatures where magazine springs operate". For all practical purposes, there is no difference in "room temperature" and, say, 500F when discussing creep in steels. I think that range more than covers the expected service temperatures. "Room temperature" is, for me, easier to reference than "temperatures where magazine springs operate".

You are correct that the high stress areas in a spring (bends, corners, etc.) can exceed the elastic limit, and this is in fact what causes springs to take a "set". This can be exacerbated by residual stresses (from machining, heat treating, coating, etc). It can take several load cycles to reach a stable spring length. In a properly designed spring this " set" would be minimized by pre-setting.

However, exceeding the elastic limit results in plastic deformation *immediately* and that plastic strain does not increase with time (unless at elevated temperature, like 700F). If at elevated temperature, plastic strain *will* accumulate over time at much lower stress (this is known as creep).

This is the critical point, and where we keep talking past each other: at these low temperatures, there is no significant creep possible. If there is permanent deformation occurring, one which does in fact depend on the length of time the spring is compressed, there is *something else* going on which has not yet been explained either here, or in the academic literature.

 

[Jlr2267]

Be specific...?

The picture/graph in your 2nd link has "time" and "strain" on the horizontal and vertical lines. Note: temperature in NOT part of the graph because the graph represents what happens with creep at "operating temp".

Um, no. The plot is a generic representation of how creep strain accumulates over time...it's not even real data, just a schematic. You won't find one that shows creep data below 700F...guess why...

I fail to see how the plot contradicts anything

Eventually, if you compress a spring long enough, the molecules will start to realign and a spring will find its new equilibrium point. That might take 1000 yrs. Or it could take a few days.

1000 years...maybe (although very unlikely)....a few days, no.
Look up the diffusion equation for metals and calculate how long your realignment takes at 100F...you'll be surprised

And as an FYI, molecules don't " realign" in creep...grain boundaries slip, dislocations and vacancies migrate through the material to reach a lower energy state. The time required for this diffusion however is astronomical at low temperatures (like where mag springs live)

However, other things such as temp, material, and how far it's compressed into its elastic range Influence how much Time it will take.

If you don't grasp that, you won't grasp anything else on the topic.

Fortunately for you I do grasp that, seeing as how I am paid to incorporate those considerations into the jet engines that carry you and your family around the world.

For giggles... what Temps do you think the recoil spring and mag spring see? What are you basing your info on?

Since the topic is mag springs, I would estimate that they would rarely (if ever) see anything more than 200F, based on my own experience. Did you giggle?

I see you're now using qualifying words like "significant" and "properly designed" as a way to give yourself wiggle room.

I am qualifying my statements because I actually know what I'm talking about, and understand the subtleties involved. A competent engineer understands that "significant" means "to a degree which would affect function." Is that good enough or do you need more definition?

What you also don't know is if the mfg decided that a spring is a consumable item and crammed more rounds into a smaller mag and thus compressing the spring deeper into its elestic range and shortening its life.

What a manufacturer does has no impact on physics. Steels do not creep in any *significant* way at these temperatures. Overloading a spring can certainly shorten its life, but creep has no part in that.

So, please tell us, how much creep, fatigue etc etc does it take to be "significant" enough to have an affect on performance of a mag spring for a glock... or a S&W... or Taurus?

If your asking how much creep strain is significant, the exact answer to that question requires FEA, along with product testing (which, by the way, I can assure you was not done by any gun manufacturer because they, unlike you, understand that creep is not a concern with mag springs).

In general, however, I have found that plain carbon steel springs (1095 for example), do not see a degradation even at 500F for 20000 hours. If you were experienced in dealing with parts that do in fact creep, you'd understand that the time required to creep even an infinitesimal amount becomes astronomical at room temperature.

 

[Walt Sherrill]

You are correct that the high stress areas in a spring (bends, corners, etc.) can exceed the elastic limit, and this is in fact what causes springs to take a "set". This can be exacerbated by residual stresses (from machining, heat treating, coating, etc). It can take several load cycles to reach a stable spring length. In a properly designed spring this " set" would be minimized by pre-setting.

So, that could explain the initial set seen with some springs. The "set" is a source of concern for folks replacing their first recoil spring -- as the new spring is always longer than the one in the gun! Magazine springs, with bends and corners certainly demonstrate that change. (You have only to buy a new Glock mag to experience it firsthand.) But so do recoil springs which either 1) don't have bends and corners, or are 2) ALL bends and corners....

Neither does it explain the softening of springs that can be observed in the examples that JohnKSa cited -- and which some of us have seen in our own weapons and mags.

John's test examples are not being CYCLED -- the springs are just being kept under a constant load/degree of compression as might be done with long-term storage of ammo in a high-cap mag. Earlier in our discussion you made the point that springs in that state weren't really working, and I think you said that such springs should not deteriorate because they aren't doing anything to cause degradation. That doesn't seem to be what's happening with John's examples, and it's seems more pronounced with the Ruger springs than the Glock. Neither of those makers have mags known for failures -- and I don't think I've ever had to replace a Glock mag spring. But that test isn't complete.

Your comments cited above also do not explain why a Rohrbaugh R9 recoil spring has a recommended service life of only 250 cycles. If the recoil spring takes a set after a relatively few cycles, why do some springs (like the R9 spring) fail later -- after several hundreds of rounds rather than several thousands of rounds as might be the case with the springs in larger guns?

I continue to argue that some springs aren't supposed to have a long life, but are intended to have a shorter life so that they can do more with less material. These springs don't work as long as other springs, but their design allows allows them to do more with less material/in less space -- a critical trait in many of the newer gun designs.

I have also stated that there may be things that can be done with some of these (arguably) sacrificial springs that will lengthen their service life. You seem to disagree -- primarily, it seems, because you don't seem believe that many of the hi-cap mags in question have the potential to degrade under normal usage (which includes long-term storage.)

You've mad a number of comments in this discussion that I've found particularly helpful. I appreciate them. But you also have shown a tendency to "argue from authority" when someone disagrees -- saying, in effect, "I'm an expert and you should believe me -- I know more than you do." You may, in fact, know more than many of us do, but that SORT of proof isn't very convincing.

You might want to try a different approach.

 

[Jlr2267]

That might take 1000 yrs. Or it could take a few days.

Actually, the 1000 yrs is not a bad estimate, if you're at 300F, holding it at the material's yield strength.

Here are the numbers for ASTM A516 steel (extrapolated of course), for time to reach 0.2% creep strain (which is a very small amount of creep by the way), when loaded to the elastic limit:

T(F), hours, days, years,
800, 2.05E+01, 8.53E-01, 2.34E-03
700, 2.98E+02, 1.24E+01, 3.40E-02
600, 1.79E+03, 7.45E+01, 2.04E-01
500, 3.56E+04, 1.48E+03, 4.06E+00
400, 5.38E+05, 2.24E+04, 6.14E+01
300, 8.37E+07, 3.49E+06, 9.56E+03
200, 6.81E+10, 2.84E+09, 7.78E+06
100, 5.56E+14, 2.32E+13, 6.35E+10

note that loading to the yield strength at 300F and holding it there, essentially baking in your oven at 300F, would require 956 years to get even 0.2% creep. I couldn't afford that test. At 100F, which is a much more reasonable estimate for the magazine spring temperature for the vast bulk of it's life, the time is 63.5 billion years.

So yeah, you'd better hurry and unload your magazine before it creeps beyond all repair

 

[Jlr2267]

So, that could explain the initial set seen with some springs. The "set" is a source of concern for folks replacing their first recoil spring -- as the new spring is always longer than the one in the gun! Magazine springs, with bends and corners certainly demonstrate that change. (You have only to buy a new Glock mag to experience it firsthand.) But so do recoil springs which either 1) don't have bends and corners, or are 2) ALL bends and corners....

Neither does it explain the softening of springs that can be observed in the examples that JohnKSa cited -- and which some of us have seen in our own weapons and mags.

John's test examples are not being CYCLED -- the springs are just being kept under a constant load/degree of compression as might be done with long-term storage of ammo in a high-cap mag. Earlier in our discussion you made the point that springs in that state weren't really working, and I think you said that such springs should not deteriorate because they aren't doing anything to cause degradation. That doesn't seem to be what's happening with John's examples, and it's seems more pronounced with the Ruger springs than the Glock. Neither of those makers have mags known for failures -- and I don't think I've ever had to replace a Glock mag spring. But that test isn't complete.

Your comments cited above also do not explain why a Rohrbaugh R9 recoil spring has a recommended service life of only 250 cycles. If the recoil spring takes a set after a relatively few cycles, why do some springs (like the R9 spring) fail later -- after several hundreds of rounds rather than several thousands of rounds as might be the case with the springs in larger guns?

I continue to argue that some springs aren't supposed to have a long life, but are intended to have a shorter life so that they can do more with less material. These springs don't work as long as other springs, but their design allows allows them to do more with less material/in less space -- a critical trait in many of the newer gun designs.

I have also stated that there may be things that can be done with some of these (arguably) sacrificial springs that will lengthen their service life. You seem to disagree -- primarily, it seems, because you don't seem believe that many of the hi-cap mags in question have the potential to degrade under normal usage (which includes long-term storage.)

You've mad a number of comments in this discussion that I've found particularly helpful. I appreciate them. But you also have shown a tendency to "argue from authority" when someone disagrees -- saying, in effect, "I'm an expert and you should believe me -- I know more than you do." You may, in fact, know more than many of us do, but that SORT of proof isn't very convincing.

You might want to try a different approach.

I can't explain every spring experiment result, carried out in every garage across America. I can only say definitively that creep is not the cause of the degradation you see.

As for my "argument from authority"... I will strongly disagree. I clearly explained (or tried to) the physics and made definitive statements which can be easily falsified (if false). Moreover, I explicitly stated more than once that I am open to a physics based explanation of this degradation phenomenon...and I'm still waiting by the way. The fact that creep is essentially nonexistent at these temperatures is fairly common knowledge, and it is not an argument from authority to state that the sky is blue...anyone can look out their window, and anyone can use the internet to learn creep basics in 5 minutes or less...really, it's not some esoteric specialty. An argument from authority would be spamming a thread with links to info which one does not understand, while expecting others to believe it *just cause its on the net*

 

[danez71]

This little know organization talks about it happening

http://www.astm.org/DIGITAL_LIBRARY/MNL/SOURCE_PAGES/DS60_foreword.pdf

An example of this relaxation limit is given in
Figure 2 for an annealed Type 304 stainless steel for
which Tm is about 800 deg. F. The remaining stress
reaches a limiting value within 100 hours for temperatures
up to 600 F (315 C) and 90% of this relaxation
takes place within 24 hours. The remaining stress is
given in Figure 2 as a function of the initial stress.
This material at room temperature has significant
relaxation which decreases with the initial stress.

Or..

http://www.db-thueringen.de/servlets/DerivateServlet/Derivate-24673/ilm1-2011iwk-064.pdf

To investigate relaxation, the springs are loaded to the prescribed relaxation tension and stored in this state at the given relaxation temperature for the given time.

At the end of this time, the load is taken off the springs and the spring force and length at the given working point again measured.

This method provides the details of both the shortening and the reduction in force which are due to the relaxation.

• Relaxation temps were 20C (about 68F aka room temp) 80C, and 160C
  
• 10270-2-FDSiCr spring steel wire.
  
• wire diameters:1 mm, 3 mm and 6 mm
  
• tempered to 350C and 450C.

2% degradation at 20C/68F/room temp in as little as ~70 hrs. (I think that was the 1mm wire)




Or.... one can look out their window and realize that the biggest reason why pianos need to be re-tuned fairly often is because of the spring steel wire stretches at room temperature.

 

[Jlr2267]

This little know organization talks about it happening

http://www.astm.org/DIGITAL_LIBRARY/MNL/SOURCE_PAGES/DS60_foreword.pdf

Thank you. This paper makes it very clear that *creep* is not the cause of relaxation at low temperatures.

More interestingly, it discuss something which may offer a possible explanation for room temperature stress relaxation in 300 series stainless steels, which may be what some folks here claim to have observed. Anelastic strain, which increases over a short period of time after load, but is recovered on load reversal.

This may actually be unique to austenitic steels, as they tend to have an ill-behaved modulus line, they strain harden like crazy, and are generally a PITA to characterize. Note that chart 1 has no data below about 700F.

I'm skeptical, however, since the paper says 304 steel has a Tm of 800F...which is an *obvious* error. Either they used another material, or they stated the wrong melting point. Either way, obvious errors like this strain credibility.

And there are other problems with paper as well, for example:

Figure 2 suggests that at room temperature, an initial stress of 24 ksi (which is ~80% of annealed 304's yield stress) relaxes to 17 ksi within 100 hours as stated in section 4.1: "The remaining stress reaches a limiting value within 100 hours for temperatures up to 600 F." This means the stress has relaxed 29% within 100 hours, at room temperature, when loaded to 80% of yield strength.

Compare the above result to the information from figure 3. This figure says that the material (cold worked 304) is loaded to "an initial inelastic strain of 0.07%." So the material represented in this plot is loaded to ~85% of its yield stress, at 900F, yet in 100 hours only relaxes about 15%.

These 2 plots therefore lead to the conclusion that stress relaxation is more severe at room temperature than at 900F! This is, of course, nonsense.

These errors in the paper lead me to the conclusion that the material represented by figure 2 very well may not be 304 steel.

http://www.db-thueringen.de/servlets/DerivateServlet/Derivate-24673/ilm1-2011iwk-064.pdf

• Relaxation temps were 20C (about 68F aka room temp) 80C, and 160C
  
• 10270-2-FDSiCr spring steel wire.
  
• wire diameters:1 mm, 3 mm and 6 mm
  
• tempered to 350C and 450C.

2% degradation at 20C/68F/room temp in as little as ~70 hrs. (I think that was the 1mm wire)

2% relative force reduction, not attributed to *creep*...the maximum reduction at the longest time recorded was 3% for room temperature...also not creep, and also not *significant*...no spring is designed so close to its functional specification that it cannot tolerate a 3% force reduction

Or.... one can look out their window and realize that the biggest reason why pianos need to be re-tuned fairly often is because of the spring steel wire stretches at room temperature.

Yes, they stretch at room temp, they experience high frequency vibrations which contribute greatly to that, BUT they do not *creep* at room temperature. A *tiny* amount of stretch can be *significant* in a piano string (changes the pitch), but we are talking mag springs, not piano wire.

 

[Walt Sherrill]

I can't explain every spring experiment result, carried out in every garage across America. I can only say definitively that creep is not the cause of the degradation you see.

I don't think I've ever mentioned CREEP, and you didn't get into this discussion until it had been going for quite a while. At post #50, you and I seemed to be almost in agreement. Others took the discussion elsewhere.

The degradation I see is -- and I acknowledge my limited knowledge of the proper terms -- is probably permanent deformation -- the state a solid exhibits when it's elastic limit has been exceeded. That is what seems to be happening with some hi-cap mags. That's also probably what's happening with the Rohrbaugh R9 recoil springs I mentioned. It may be what's happening in JohnKSa's tests. I suspect that's what happens when a coil spring softens with use, over time. And that is, I suspect, what Wolff Springs guideline is intended to postpone or delay -- through downloading a round or two. They may suspect that SOME springs are sacrificial. But if a downloaded spring isn't sacrificial, downloading won't really hurt; if it is sacrificial (when fully loaded), downloading will postpone the inevitable.

You've said that unless a spring is working, things can't change. I wonder: if a spring is depressed far enough to exceed the spring materials elastic limit, and the spring material starts to permanently deform, doesn't THAT become a subtle form of work? (If it's NOT work, why is it damaging the material? Is some minimal amount of cycling required before permanent deformation can occur? That may be the part I'm overlooking...)

I suspect that the longer a magazine spring or recoil spring is subjected to the stress that causes the spring material to exceed it's elastic limit, then more and more of the springs material will be deformed as the remaining material experiences the same stress/work/pressure, etc. that was once handled by a greater supply of non-deformed material.

I don't think that permanent deformation happens instantly or uniformly throughout the material, and as you've noted in earlier replies, loading and working the spring puts different loads on different parts at different times. Cycling the springs does the same, as will reloading the mag before it is completely empty, etc. Many, many variables can affect what happens.

Do coil springs soften or just break? (I'm not trying to force an either/or choice, there. Answer however you like.)

Bill DeShivs, a knifemaker who talks of his experience making springs, says properly made springs should break, not soften, and then only from being worked. What's YOUR position on that point? Bill doesn't seem to embrace the concept of springs made to work well for shorter periods (i.e., sacrificial springs.)

How does failure in a coil spring manifest itself if it does fail (for whatever reason)?

 

[Jlr2267]

Do coil springs soften or just break? (I'm not trying to force an either/or choice, there. Answer however you like.)

They can do either, or both, depending on the conditions of temperature history, load history and material properties.

When springs develop microcracks, they can "soften" because the cracks lower the effective modulus of the material. These cracks can grow, coalesce and eventually the spring breaks.

One of the links posted by danez71 suggests that there can be a small amount of room temperature stress relaxation at very high stress (relative to yield strength), which would "soften" a spring. For the application of a magazine spring however, 2-3% loss in spring force would seem to me insignificant.

Mechanical compression springs are generally designed to be at only a fraction of yield strength when fully compressed (40% is a generic upper limit). In critical applications, they are also "preset". My guess is that mag springs are not designed as critical components and are somewhat of an afterthought.

 

[danez71]

One of the links posted by danez71 suggests that there can be a small amount of room temperature stress relaxation at very high stress (relative to yield strength), which would "soften" a spring. For the application of a magazine spring however, 2-3% loss in spring force would seem to me insignificant.

Mechanical compression springs are generally designed to be at only a fraction of yield strength when fully compressed (40% is a generic upper limit). In critical applications, they are also "preset". My guess is that mag springs are not designed as critical components and are somewhat of an afterthought.

Thats the point that Walt, and then me, we're pointing out a couple of pages ago and you refused to acknowledge.

Regardless, I'm glad we've come full circle in under 4 pages.

3% may be significant in some designs... I don't know and I'm not going to spend the time to figure it out.

However, making a blanket statement saying all mags can be loaded full indefinately and have no negative effects is not accurate.

You mentioned 40% above. I can say with some authority that Hughes uses 25% for many space applications with "indefinately" as the life span goal.

It can be done with springs.... but all mag spring aren't designed with the same level of safety margin as is designed into flight and space applicatons.

 

[GLOOB]

That's also probably what's happening with the Rohrbaugh R9 recoil springs I mentioned.

Rohrbaugh states that the spring should be replaced every 250 cycles? Do they make any mention of how LONG you can leave a magazine loaded before replacing the spring?

I think the Rohrbaugh mag would be a perfect garage experiment to see how leaving a "sacrificial spring" loaded affects its performance.

It would be pretty lame if a Rohrbaugh could only be loaded for, say, 7 days at a time, lol. So to me, it seems like the R9 example is supporting what Jlr2267 has been saying all along. Replace after # cycles, not amount of time.

Also, re: piano example. The biggest reason for pianos going out of tune is probably warping of the wood frame, don't you guys think?!

 

[Jlr2267]

However, making a blanket statement saying all mags can be loaded full indefinately and have no negative effects is not accurate.
.

Well, I do concede that there is some amount stress relaxation, even at room temperature. I do however think the available data suggests it is limited to roughly 1%-5%, which shouldn't be significant in a robust design (but then again mag springs are probably not that well thought out).

My apologies if I came across as a pompous a-hole...not my personality at all...just let the frustration get to me.

 

[GLOOB]

They way I see it, it may be a good thing to leave a mag loaded for an extended period when you first get it.

If the spring was not thoroughly tempered, and you let the stress relaxation occur through use, the spring will start to give at one specific spot, first. The rest of the spring is still "stronger" with the "new spring feel" than the initial "weakest link," hence that point will bend more than the others as you are loading the mag. Do you want to repeatedly cycle that mag partway (by downloading it) many times before the entire spring has relaxed? Repeatedly "aging" one point faster than the rest of the spring? Or do you want to let it sit at maximum compression until the whole spring is destressed? If you download it by one or two, you're only bending a couple of points on that spring all the way (or possibly even more than all the way!), and the rest won't begin to "take a set" until you load it all the way for the first time.

Ideally, the spring will be thoroughly heat tempered before it is installed, which will destress the entire spring, equally. But if it's not tempered enough, you could get into the above situation maybe? To me, this must surely be one of the reasons you need to temper a spring to begin with. Otherwise, you could just use if right away (albeit at a higher initial weight), and eventually the stresses would be relieved over time, at room temperature. But this is not the case... what happens is the spring is more prone to breaking - through repeated cycling, NOT from sitting still.

I dunno. I know that I leave my mags loaded fully. If that makes them stop working, I want to know sooner rather than later. If my mags don't work after fully "taking a set," I will figure out what springs and how many rounds WILL work for those mags, I guess. If I'm going to download a mag, it's because I am going to do so ALL the time. Not just for storage.

 

[Jlr2267]

They way I see it, it may be a good thing to leave a mag loaded for an extended period when you first get it.

If the spring was not thoroughly tempered, and you let the stress relaxation occur through use, the spring will start to give at one specific spot, first. The rest of the spring is still "stronger" with the "new spring feel" than the initial "weakest link," hence that point will bend more than the others as you are loading the mag. Do you want to cycle that mag many times before the entire spring has relaxed? Repeatedly over-bending and potentially fatiguing that point? Or do you want to let it sit at maximum compression until the whole spring is destressed? If you download it by one or two, you're only bending a couple of points on that spring all the way, and the rest won't "take a set" until you load it all the way for the first time.

Ideally, the spring will be thoroughly heat tempered before it is installed, which will destress the entire spring, equally. But if it's not tempered enough, you could get into the above situation maybe? To me, this must surely be one of the reasons you need to temper a spring to begin with. Otherwise, you could just use if right away (albeit at a higher initial weight), and eventually the stresses would be relieved over time, at room temperature. But this is not the case... what happens is the spring is more prone to breaking - through repeated cycling, NOT from sitting still.

I dunno. I know that I leave my mags loaded fully. If that makes them stop working, I want to know sooner rather than later. If my mags don't work after fully "taking a set," I will figure out what springs and how many rounds WILL work for those mags, I guess.

I've never replaced a spring on mags I keep loaded like my HD guns (loaded for 16 years, shot very little). I have frequently replaced springs in various range gun mags however (lots of loads/unloads).

 

[moxie]

Some non-scientific observations:
1. While I personally have never had a magazine spring (rifle or pistol) fail due to being fully loaded for an extended period, it's clear from many of the posts in this and other threads that it does seem to happen. What's missing is any analysis of make, model, type of gun/mag/spring, time loaded, etc. So all we've got is a lot of anecdotes. Take away seems to be: if you've got a weak spring, change it.

2. Here's a war story for your reading pleasure. In Vietnam, for perceived safety reasons many Army armories stored 1911s with slides locked to the rear hanging on wood pegs through the trigger guard. This obviously kept the recoil springs smashed pretty tight, often for long periods. I fired some of these guns and was plagued with a lot of failures to go into battery. A tap on the back of the slide fixed the problem. Clean guns, well lubed, GI ammo. I figured out it was the recoil springs. You could feel they were wimpy when racking the slides. Changed them out and voila! No more failures. This is obviously not a scientific experiment but does show anecdotally that some coil springs do lose their springiness (there's physics for ya) when kept squashed for a while. I have no idea whether mag springs (all/some) are made the same as recoil springs (all/some) and thus prone to the same vicissitudes.

 

[GLOOB]

I think my post #90 can explain why springs seem to take more set over a longer period of compression.

In a mag, the spring is not compressed quite all the way, to the point where each coil is physically resting on top of the other (otherwise the mag wouldn't fit in the gun; well, maybe some 8 rd 1911 mags are an exception. ). The weight of the spring is not exactly the same across it's entire length, and any residual stress will take time to resolve.

So at first, when fully loaded, there are some points on the spring that are bent more than others, due to asymmetrical distressing of the entire coil. So when you remove the spring, it's longer, because some parts of that spring are still not distressed all the way. Over enough time under compression, the distribution may become more even, and more of the spring will be fully distressed? This is simply the initial distressing of the spring, not creep, I guess. I'm a little out of my depth in this discussion.

 

[danez71]

This is in response to post89 by Jlr2267

I totally agree.

I think mags for service pistols designed for military will more than likely have enough margin built in to not be affected by 3%. Compacts and micro designs is when things gets sketchy.

For the record, I've never changed a mag spring.

Pompous a-hole? Maybe a little ... but we all have it in us. Maybe I just stumbled a new friend.



I've been using my phone the last couple days to post so that explains 1\2 my screw ups and typos.

 

[Walt Sherrill]

They can do either, or both, depending on the conditions of temperature history, load history and material properties.

When springs develop microcracks, they can "soften" because the cracks lower the effective modulus of the material. These cracks can grow, coalesce and eventually the spring breaks.

That makes sense, and it probably explains why we don't see many broken coils springs in handguns -- because if they get soft and they don't perform well, they will be discarded BEFORE the cracks can grow, coalesce, and the spring material break. (Car coil springs may be different, because a car can still drive with weak, maybe slightly sagging springs. They can carry heavy loads and hit big bumps, etc.. for a long time... and then they can break! )

Mechanical compression springs are generally designed to be at only a fraction of yield strength when fully compressed (40% is a generic upper limit). In critical applications, they are also "preset". My guess is that mag springs are not designed as critical components and are somewhat of an afterthought.

I suspect recoil springs are also not a primary focus for most gun makers. The last sentence cited above states an idea I've been thinking about since this discussion got into full swing. Your work experience with metals and their application in the aerospace industry has been with highly specialized needs and sophisticated materials that must meet very high standards. As you say, a lot rests on the proper function of a jet engine. Recoil and mag springs that seem to be an afterthought are probably a sign of practical BUSINESS hurdles that are hard to overcome: designers in much of the firearms industry, given market size and revenues, probably don't have deep-enough pockets to find or develop better ways to get the "spring" job done.

I also suspect that most of the changes we've seen in firearm spring usage over the past 20-30 years has had more to do with how springs are USED than changes to or advances in how they are made or what they are made of.

A sacrificial spring probably wasn't "needed" until they started making very small center-fire weapons and the buying public started pushing for much smaller but still high-capacity guns. (And, it seems that a "sacrificial" spring was needed only because there was no obvious way to achieve appropriate function in the space available...) Some of the new, smaller guns were developed by small firms that simply don't have pockets deep enough to develop a new class of springs (if that is even possible.) I'd argue that Kel-Tec is emblematic of that segment of the firearms industry. But, even the bigger firms like RUGER or S&W may have a tough business case to make if they propose doing heavy R&D for spring applications.


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[HexHead]

I do change my oil every 3,000 miles, cheap peace of mind.

I change magazine springs if they need it, they're cheap too.

Silly me. I follow the car manufacturer's recommendation, not the oil change marketing department's recommendation. What do those engineer's and designers know?

 

[JohnKSa]

My apologies if I came across as a pompous a-hole...not my personality at all...just let the frustration get to me.

You pointed out some holes in my original experiment which is good. The new test will be more exhaustive and will have good control data for comparison.

I've got my new spring tester about 50% done and will start the test when it's ready. If everything goes well, we should have some results to discuss in 6 months or so.

 

[Walt Sherrill]

I'm very glad that Jlr2267 has joined the group and is contributing to the discussion. He brings a different perspective and adds to the base of knowledge here. That also means we've got at least three engineers participating from time to time, and a couple of them have more specialized knowledge of the topic. We've also had a metallurgist involved in the past.

Many of us look at OUR experience with things, and assume that our experience is typical. But those who shoot OPEN classes, compete with very hi-cap guns/mags, who carry pockets guns, or who ONLY shoots 1911s, or messes with a very small center-fire pistol (like the Rohrbaugh R9) bring a different base of experience to this type of discussion.

Re: spring replacement:

I've had to replace a few mag springs, over the years, but never in a full-sized gun that held fewer than 15-rounds. (When I was actively doing IDPA, I picked up a bunch of cheap 10-round mags and used them a lot, and they never seemed to hiccup; some of them saw a LOT of use.)

I once sold a Kahr P9 with 6-mags. I had bought it used, with those mags and two holsters. I shot it some, carried it a little, function-tested it periodically, and did so again before the sale, using 4 of the 6 mags. It seemed to function well then, and had never been a problem.

Soon after I sold it the buyers said that all 6 mags wouldn't feed properly. The buyer wanted to return the gun and get his money back. While it was a "local" FTF sale, we both still had to drive about 50 miles. The gun sale included an unused Alessi IWB holster which came with the gun when I bought it. I told the new buyer the problem was probably bad mag springs and that I would replace them at my expense, but he didn't trust the gun. He got his money back and I got the gun back. I ordered 6 new springs for the Kahr from Wolff.

When I installed the new springs I was astounded by the difference between the strength of the old and new springs. The old springs were very soft and easily flexed, but it was a CHORE to get the new springs installed, and I thought I would need a bumper jack to get them into the mag tube! More than one of the springs flew across the room several times as I mishandled the installation process. I don't know what might have happened to cause their rapid deterioration -- unless the new buyer did something to stress the springs, like stretch them because he thought they were not strong enough.

The mags were easy to load when I had the gun, but functioned properly. Once the new springs were installed the gun was 100% again -- but much harder to load. Soon after that I sold the gun and mags again (without the holster) for the price I had originally asked -- which was more than I paid for everything -- and never had a callback about feeding problems.

I later sold the Alessi holster separately for $150 on Ebay. (I woke up and did a little checking and found that Alessi holsters are much in demand and can be quite pricey.) Duh...

 

[MICHAEL T]

My Bersa Thunder is 10 years old I have use the same mag since new Its kept fully loaded and shoot about every 3 months. I ordered 2 extra mag springs when I got the pistol. Their still not used.

 

[fletcher]

If there is permanent deformation occurring, one which does in fact depend on the length of time the spring is compressed, there is *something else* going on which has not yet been explained either here, or in the academic literature.

Time for me to jump back in. Permanent deformation at room temperature by stress relaxation in springs has been addressed in academic literature since at least the 1970's. This mechanism is completely different from both fatigue and creep. You are correct that creep is not operatimg in any significant capacity at spring operating temperatures, but relaxation does occur - I have made posts in similar threads to this effect with references to papers showing effects.

One such thread.

In short, permanent deformation does occur in springs under constant load at room temperature. The extent of this deformation depends on alloy, stress, temperature, and time. For most good magazine springs, the effect is minimal. However, there are plenty of users reporting weakened springs which may have used less-than-optimal design or materials.