Recoil Spring Longevity

[chack]

I'm really curious about this:

1) Why doesn't anyone change the springs on their rifles?
2) Why is it that some of y'all change out recoil and mag springs but not extractor, firing pin, and sear springs?

I think that the most likely answer is because the recoil and magazine springs are so easy to replace. A striker spring failure will disable a gun just assurely as a mag or recoil spring. If the gun was so poorly designed that one spring will fail before the effective service life of the gun, why is it that the others won't?

[Bill DeShivs]

Walt-
Did you read the entire article?

[Bill DeShivs]

Here is someone who seems to agree with me: http://www.civil.columbia.edu/adjunc...g/faculty.html

And here are his views on spring fatigue: http://yarchive.net/gun/spring_fatigue.html

Though the archived information is hard to decipher. You must understand that this is a conversation, and lines are interjected.

[Scimmia]

Nope, he doesn't:

Since fatigue is a failure mode due to CYCLIC loading,
your observation does not indicate fatigue failure. A
loaded magazine is a static situation, not a cyclically
loaded one.

He specifically says that fatigue can occur with cyclic loading of the spring, which is exactly what happens to a recoil spring. He's making the point that a spring sitting in a static state (loaded magazine) won't fatigue, which has been said many times already in this thread.

[Bill DeShivs]

He also says that fatigue leads to embrittlement and breakage-not weakening.

[Scimmia]

Where? The only time I see him talk about that is in regards to plastic deformation, not fatigue.

[Scubasimmons]

Article is wrong constant stress below the yield limit will result in creep. You do not need to exceed the elastic limit to experience creep. Do I think creep affects gun spring? Hopefully it's accounted for in the design. But creep does happen.

[Walt Sherrill]

Bill: I did read the whole article. Show me something other than opinion, or statements that don't contradict themselves. Show me something based on actual testing, or give us some proof via technical references.

I've also agreed (and asserted) time and again that many springs may outlast the shooters or the guns in which they are installed. But I know from first-hand experience that some won't. As do others, here.

If some springs won't last forever, as you would have us believe they would, and if , as you claim, springs are springs, why are those particular springs NOT able to live as long as their longer-lived brethern? Early on you claimed it was due to badly/cheaply made springs. Perhaps that is a problem with some of them, but I don't think it's a problem with all of them.

Could it be that some guns just push springs harder or farther than others, and those applications, by their very nature, shorten the spring life as a consequence? When spring makers (like WOLFF) say that keeping springs fully compressed (at, or near their design limits) will cause them to degrade, I give that expert opinion more credence than when a gun maker says otherwise. Most standard (non hi-cap) mag springs are never fully compressed, and most hi-cap mag springs are frequently (nearly) fully compressed.

When spring makers like Wolff tell us how to preserve spring life (by downloading a round or two for long-term storage), they don't seem to be trying to sell more mag springs. It might be they're trying to tell us something important.

Do YOU believe that springs heal by being rested? Some of your "experts" seem to be leaning in that direction. And when a company's customer service rep makes a general statement about all magazines (not just his company's mags), I get really skeptical.

If you'll remember, we've also had a couple of police armorers participating in earlier versions of this same discussion who have talked about having to replace mag springs in a lot of police guns that have been kept fully loaded for extended periods. Is that credible evidence for this discussion, or just another example of inferior product? Just bad springs, do you think? Some of them were S&Ws, I suspect.

The last time we had this same discussion, you wrote -- amending your earlier statements -- that springs could fail when pushed to or beyond their elastic limits. That's what Wolff said. You now seem to be turning your back on that statement. Are you changing your position, again? I'm sure I can find that statement and others by you, to that effect. This forum has a long memory.

Another of your new expert sources says springs won't fail -- but then goes on to say that the gun may not function properly -- may not feed the next round, etc. Isn't that the description of a spring failure? He seems to think that some springs can go soft and it's not a failure, but only a break is a failure.

You still haven't answered an important question: why do some gun makers tell their customers to replace sub-compact and compact recoil springs far more frequently than the springs used in their full-sized guns? Springs are springs, aren't they? Are they now designing inferior guns, or are they just using springs, like bullets, as expendable resources?

SCIMMIA, in responding to Bill's citation, wrote:

He's making the point that a spring sitting in a static state (loaded magazine) won't fatigue, which has been said many times already in this thread.

That HAS been said, but said both correctly and incorrectly.

The technical information we've seen posted here suggests that some springs compressed in a static state (as in a WWII 1911 mag that is fully loaded) will often not deteriorate enough to ever be noticed. That's because that particular "static, compressed" spring isn't being asked to remain static near it's elastic limit. There's more room to compress those springs, and they're not being asked to work as hard as they could be worked! (I think an 8-round 1911 mag uses the same springs as a 7-round 1911 mag, for example. Some room there for further compression, to be sure.) Which of those springs is being compressed more, when held static while fully loaded? It IS working, because it's trying hard to LIFT those rounds, and as soon as it's allowed to lift them (by the slide moving back, extracting a spent round and moving forward to pick up a new round, it WILL lift one into position. It's static, but it's working!!)

Wolff (the spring makers) and others say that if the spring is fully compressed, and that full compression pushes the spring to or beyond it design limits, there can be deterioration. That's apparently why some hi-cap mags springs (for 15-18 round mags) seem to die faster than the springs for 10-rounders. That's also probably why some springs in compact mags (which are the equivalent of a high-cap mag in a smaller case) don't last as long.

There may also be why some SMALL RECOIL springs for compact guns don't last as long -- or maybe it's because they're being forced to do more work than normally can be done by a spring that must fit in that smaller space.

Please note: those "hi-cap" or "compact" springs are not cycling more often than their bigger brothers, but they're being called upon to do more work with what is probably less steel and fewer coils than their larger relatives. I would think that cycling/compression alone isn't NECESSARILY the killer you think it is, but must also be coupled with the amount of work being attempted by that spring.

As has been noted before, if compressions/cycles alone would kill springs, a heck of a lot more tappet springs ought to have died, by now, than have died. (My nephew had a Toyota pickup that he put several hundred thousand miles on, and then sold to a friend. It's still running strong and is nearing 500,000 miles without a major overhaul or new tappet springs. That's a LOT of compressions. I suspect it's a good bit of oil out the tailpipe, too, now.)

Working a spring can certainly cause it to deteriorate, but if it's properly designed and kept within its design envelope, it may live a very long life despite those cycles. It'll deteriorate, but not enough to matter.

If so, the number of cycles its subjected to may not be as important as the amount of work performed during those cycles -- how far the springs must compress, and how much work it must do during its work cycle. That may be why full-size 1911 recoil springs last a long time, while smaller recoil springs in compact versions of the same gun -- handling the same rounds -- don't last as long.

.

[JohnKSa]

Bill,

Chang's article is actually a refutation of the claims in another article. His refutations are indented while the original article is justified against the left side of the page.

He does, in fact, acknowledge that springs do weaken-- he uses the term fatigue.

"However, fatigue can definitely occur due to cyclic loading below the static yield strength of the material. Even absent surface stress risers (e.g., notches), fatigue crack nucleation can occur at grain boundaries, second-phase particles, twin boundaries, and other microstructural features which exist normally."

However, he also believes that springs can't be weakened by simply compressing them and leaving them compressed. That, unfortunately, is demonstrably false. I've seen at least two experiments with carefully measured results (one of which I've posted on this thread) demonstrating that under certain circumstances leaving a spring compressed can weaken it and leaving it compressed longer weakens it more. The effect is not only repeatable, it tracks well between the variety different springs tested showing that it's fairly consistent across a number of springs of varying manufacture and quality.

Originally Posted by Scubasimmons

Article is wrong constant stress below the yield limit will result in creep.

I agree, there's simply too much experiential and conclusive experimental evidence to conclude otherwise.

Originally Posted by chack

Why doesn't anyone change the springs on their rifles?

First of all, no one has said that no one changes their rifle springs.

Second, there are very few centerfire rifles that have "recoil" springs. That is, the springs are not absorbing "recoil", they are simply bolt return springs. That's a much less stressing job for a spring.

Why is it that some of y'all change out recoil and mag springs but not extractor, firing pin, and sear springs?

How many manufacturers recommend replacement of extractor, firing pin and sear springs on a regular basis? Off the top of my head, I don't know of any. On the other hand, I know of several manufacturers who formally or informally recommend replacement of recoil springs on a regular basis based on the number of rounds fired. I just finished reading an article about a new Kimber compact pistol that indicated that Kimber recommends replacing the recoil spring every 1000 rounds but made no mention of other springs that needed regular replacement.

For what it's worth, I don't replace magazine springs on a regular basis although I would if I found I were having repeated failures at reasonably regular intervals or if a manufacturer were to recommend a replacement schedule.

[Bill DeShivs]

Wow! Seems everybody's a spring expert!
I have researched this a little (VERY little!) and it seems you can find an expert that will agree with you no matter what your stance.
It just leaves me with more questions. Why haven't all the 1979 Toyota springs collapsed? They are all made pretty much the same. Why don't "weak" springs just keep getting weaker, until they're like noodles?

Walt- I agree that over compressing springs ruins them. My position has not changed- Properly manufactured and designed high carbon steel springs should not "get weak" unless they are stressed beyond their elastic limit, are rusted, or are over heated. My contention is that cycling work hardens springs, causing them to break, not get weaker. Some gun designs obviously over stress springs.

Do some springs act differently? Probably so, but I still don't understand why!Some say "creep" and other experts say creep does not happen at room temperature.

[JohnKSa]

...it seems you can find an expert that will agree with you no matter what your stance.

Unfortunately, that is true. A lot of the problem is people like "John S. Layman" who pretend to be spring experts but won't even sign their real names to the authoritative-sounding articles they write.

Things get a little less confusing once the experts are filtered down to people who actually do controlled experiments and record measurements and provide experimental evidence to support their opinions.

Experts (at least some experts) may not be able to explain WHY springs weaken or why springs only weaken a certain amount and don't turn into noodles. They may differ on the specific mechanism that causes spring weakening. It may even be possible to find some "experts" who still claim that springs don't weaken.

But we have access to experimental results (RBest's spring test) that demonstrate conclusively that springs DO weaken under certain circumstances. That means there's no longer any need for (or point to) debating the question of whether it's possible for springs to weaken without breaking. Especially since a second party (Tom Gaylord in the R1 book) has done a similar experiment with a different variety of springs with the same findings.

[chack]

Second, there are very few centerfire rifles that have "recoil" springs. That is, the springs are not absorbing "recoil", they are simply bolt return springs. That's a much less stressing job for a spring.

I don't understand the difference between the work an AK, SKS, AR, FAL recoil/buffer spring does in cycling after each round and the work that a pistol does doing the same thing.

Blowback firearms excluded.

I'm not trying to be argumentative, I just want to be able to understand the reasing behind someone that thinks changing their springs after as few as 500 rds.

I've fired 500 rounds in one range trip before and I'm sure there are hundreds of members here that have fired pistols way more than me.

In fact, I don't think I've even fired 10,000 rounds through pistols in my entire life. I'm just not that into them. We hardly ever shoot them in the Army, I only have a dozen or so, and only started collecting the after Obama got elected and I became afraid he'd try to make national gun laws like Chicago's. I've fired more than 20 times as many rifle rounds and own several times more rifles than handguns, so I am really paying attention to this and trying to keep an open mind.

I've changed 1 recoil spring in all that time, on a blowback 9mm rifle that is known to have a poorly designed spring/buffer combo.

I'm willing to concede that there is some weakening of a spring as part of a gun's break in. I think that a properly designed spring takes that into consideration in the design.

If a gun requires a spring pressure of 15-30 pounds to operate properly, I thin any good engineer will design enough of a margin for error to allow the 25# factory spring to be well over the minimum strength after a 20% decrease in strength due to a weakened spring.

Consider this:

If your gun is 100% reliable and you put a new spring in it, can you be completely sure that the new spring isn't TOO strong? It's perfectly concievable that an odd round may not have enough charge to fully cycle the new 25 pound spring but it would have cycled the slightly weaker old 20 pound spring.

[Carry_24/7]

I believe in following a manufacters recommendation for maintenance, or all bets are off for reliability.

Now, that does not mean I ALWAYS do. Even for my 1911, it states that it was made for ball ammo, yet I shoot all types reliably. I also do not believe in rotating tires on cars.

I have previously stated that I do not buy used guns because I don't trust them, thats not entirely true. I have shopped for used guns, but always hesitate because of how I know some folks treat their weapons, especially cleaning & lubrication. But if I ever find a really good deal on a used gun, i'll buy, but I believe i'll always look on it a little "differently."

[danez71]

Quote by John

I've repeatedly provided a link on this forum and others to test results showing that compressing springs can eventually cause them to weaken.

And I have provided numerous links and data for Bill in a few other threads over the last few months. Bill just doesnt want to acknoledge it.


Quote by Bill

John,
My purpose is not to be argumentative.
Nor are my methods scientific.
Obviously some springs fail, but I have not seen it, except as I noted. I certainly don't understand why.
If springs get weak, how weak will they get? Will they completely collapse?
Here is a very simple experiment to understand why I say this:
Take a piece of steel wire (spring wire, if you have it,)and bend it repeatedly in the same spot. Tell me if it gets noticeably weaker, or if it breaks. __________________

But Bill, thats exactly what you're doing... being arguementitive; or possibly just in denial.

Youre right, your tests are not scientific. So why wont you take to heart any of the scientific data that has been provided to you numerous times?

You admit youve some springs fail, and you dont understand why. Try reading all of the links and data that has been provided numerous times, with an open mind, and you might start understanding.

I used to race RC cars. Some designs use spring wire for suspension and steering. I can tell you that the spring wire doesn fatigue.


Not only that, but I provided you a link with data using various metals of spring wire and it gave a nice chart of fatigue of the verious spring wires at various temps.

The data I provided even came from a spring manufacturer.


You refuse to recognize and accept any scientific data provided and instead just keep saying 'I havent seen it' and now admit that you dont understand.

And quit bring up leaf spring in knives or cars.

[zukiphile]

Bill, you and I had this conversation a few years ago, and it took me a couple of posts to get you to flesh out what you meant. I think you confuse people when you write something like "Springs are springs", implying that all springs are the same.

You don't believe that all springs are the same or that different applications might not have them deteriorating differently, as idicated by the bolded language below.

Originally Posted by Bill

My position has not changed- Properly manufactured and designed high carbon steel springs should not "get weak" unless they are stressed beyond their elastic limit, are rusted, or are over heated. My contention is that cycling work hardens springs, causing them to break, not get weaker. Some gun designs obviously over stress springs.

What makes you position problemmatic is that you don't state the limits of your assertion when you start this argument with people, and argue about springs and applications that you do not know are within your subsequently stated limits.

People in these threads have not been discussing leaf springs in your hand-made folding knives. That seem painless enough to ackowledge.

[Hawg]

I have owned a lot of guns over the years. I've had to change two springs in my lifetime. One in an 1884 trapdoor because the original broke and one in an old Savage .22 made in the 30's that's had untold thousands of round fired through it. In short, a springs longevity is way longer than yours.

[OJ]

#71
OJ
Senior Member

Join Date: December 24, 1998
Location: COLORADO SPRINGS, CO, USA
Posts: 1,400

Dunno if it was needed but a couple of years ago on my Colt's Government Model Series 70 - made in 1970 - the slide stop slid down locking up the action at the range.

Checked with Wolff Springs for a stronger - well at least newer - firing pin spring - found they had a package deal that included both recoil spring and firing pin spring - well - you know how things like that go - I ended up buying two of those. Original had over 7K rounds through it and the repro over 5K. I guess my long life as a surgeon led to to view it as "preventive medicine" -

Looking back, I could have made my reasoning for replacing both springs as I did when only the firing pin spring was the one giving problems.

I realize asking a company that makes springs if I need a new one may be somewhat like asking my barber if I need a haircut -

However, there was a bargain price, as I recall, and there didn't seem to be any negatives associated with replacing the recoil spring when I replaced the firing pin spring that was not up to the job - and, if the recoil spring wasn't doing its job as good as it should, I might not recognize that and the results (possible slide-frame battering) could be more serious to my 1911 than the worn firing pin spring letting me know it needed replacement by letting the firing pin stop slide down.

Seemed like a good idea then and there didn't seem to be any down side to changing the recoil spring.

[chack]

I'm reminded about a buddy that started doing trigger jobs on his handguns. He did his XD and it was great, got it down to 5 pounds. then his glock and his dad's sigma. he dot the sigma down to just under 5 pounds and it was really nice, until he took it to the range.

With the factory striker spring he never had a misfire, but he showed me a dozen rounds with light primer strikes that didn't fire. He went back to the original used factory striker spring and never had another malfunction. The trigger pull is just over 5 pounds now.

When he did the trigger on my Sigma I made sure he didn't mess with the striker spring.

If it ain't broke, don't fix it!

[Walt Sherrill]

Walt- I agree that over compressing springs ruins them. My position has not changed - Properly manufactured and designed high carbon steel springs should not "get weak" unless they are stressed beyond their elastic limit, are rusted, or are over heated. My contention is that cycling work hardens springs, causing them to break, not get weaker. Some gun designs obviously over stress springs.

I'll ask again: why would the maker of a compact or sub-compact 1911 recommend replacing recoil springs in the compact models far more frequently than they recommend for their full-size guns? If, as you claim, springs are springs, aren't we required to assume -- based on your analysis -- that gun makers, like Bill Wilson, aren't using "properly manufactured and designed high carbon steel springs" in their smaller guns, even though they continue to use high-quality materials in their full-size guns. Wonder why they'd use inferior materials in one type of gun and not another? Another participant here said it was cycling that killed springs. If so, why does 2000 rounds almost kill a sub-compact 1911 spring, but not the recoil spring in a 1911 Government model? They are arguably the same materials and the same number of rounds fired...

Perhaps the answer is simpler than we think. I wonder if the springs in some sub-compact guns (and in hi-cap and compact mags) -- and maybe in other gun designs as well -- are being routinely pushed to and past their elastic limits out of necessity. Perhaps modern-day metallurgy hasn't advanced at the same pace as gun design -- and spring makers can't build long-lived springs that will fit in the space available in some gun designs and still get the job done.

I wonder, too, if coil springs in hand guns are stressed differently than the leaf springs in knives?

With coil springs, the load/stress/wear is clearly distributed over a lot of different bends or coils in the spring. It would be difficult to get enough pressure on any one point to make it break there, as the work load is really widely distributed, by by the nature of the spring! Then, too, nearly all of these coil springs must both bend AND twist during their work cycle, which may not be the case with leaf knife springs. Perhaps the load/stress is more focused in a leaf spring used in a knife, making a single-point break more likely?

I wonder if pushing some types of coil springs to or beyond their elastic limit leads to many, almost invisible micro-fractures in the steel, thereby reducing the strength and functional diameter of the steel coils? If so, the spring would become effectively smaller, would look the same, but wouldn't be able to perform the same amount of work. If that happened, a spring getting "softer" might really be the result of many (thousands?) small breaks -- a theory consistent with your experience with spring steel. Proving that to be the case would be difficult without destructive examination by people with the right equipment and analytical skills.

It may be, too, as suggested above, that leaf springs, by their nature (how they are used), focuses their work effort more narrowly than do coil springs, so that they'd break more readily at a critical point, rather than "soften" (i.e., break more broadly).

Some folks here keep citing their own long-lived springs as examples of all springs. I would remind them that while springs may be springs, not all springs do the same kind of work or handle the same kind of loads. And, more importantly, not all springs are PUSHED to their limits.

Where's BernieB (whose analysis was cited in an earlier post) when we need him?

[Walt Sherrill]

Checked with Wolff Springs for a stronger - well at least newer - firing pin spring - found they had a package deal that included both recoil spring and firing pin spring - well - you know how things like that go - I ended up buying two of those. Original had over 7K rounds through it and the repro over 5K. I guess my long life as a surgeon led to to view it as "preventive medicine" -

Wolff typically includes firing pin springs with recoil springs, giving a matched pair. Heavier recoil spring, heavier firing pin spring.

We should note, however, that the firing pin spring RETARDS and RETURNS the firing pin and doesn't make it slam forward harder. The idea with the firing pin spring replacement, especially with heavier recoil springs, is to avoid INERTIAL movement of the firing pin when the slide slams forward, or when the gun is dropped.

Wolff has been doing this for years, but it's probably an unneeded practice with many modern guns -- since most newer guns have firing pin blocks, and that firing pin isn't going anywhere until you pull the trigger. With a firing pin block in place, an INERTIAL discharge isn't very likely or even possible. Ditto a discharge from a drop, etc.

[Bill DeShivs]

Not feeling well today. Maybe I'll be up to discussing this more tomorrow.

[danez71]

Well said Walt.

On some of your points....

Ive been talking to my 'eal engineer contacts again and I got some good rough info.

The amount of compression of a spring that will optimal for spring life is 0% compression. The worst is 100%. It is not a linear rate of degradation.

Dependant on overall design, some where around 25% compression max is where he keeps his designs (aerospace related, not gun related) in oder to meet his requirements of longevity which are, of course, dependant on application (his applications usually have a 10 yr life min at X cycles per year)

During this conversation, up came several applications that generally meet this 1:4 compression.

Car coil springs: most car only have around 4-6" of suspension travler but their spring are usually well over a foot long. Look how long a ball point pen spring is compared to the needed travel amount. Auto valve springs... they only compress around 1/4" but are all over 2" long (all of the ones Ive seen anyways). Not surprising was that knives were not mentioned.

Coil springs are essentially a long torsion spring but in the shape of a coil.

I can say that if you google "chevy lean", one will find tons of hits of people complaining that their torsion sprung silverado leans to the drivers side even with-out a full tank of gas. I also know for a fact that GM has a acceptable range of ride height that the spring has to be able to accomplish.

Walt said:

Perhaps the answer is simpler than we think. I wonder if the springs in some sub-compact guns (and in hi-cap and compact mags) -- and maybe in other gun designs as well -- are being routinely pushed to and past their elastic limits out of necessity. Perhaps modern-day metallurgy hasn't advanced at the same pace as gun design -- and spring makers can't build long-lived springs that will fit in the space available in some gun designs and still get the job done.

This is the right answer right here. I'll make one addition. People need to stop thinking of this as "past the elastic limit" issue.

The greater % of compression as compared to the length of the spring in its natural state... the quicker it fatigues. As mentioned above, this is not a linear rate.

[JohnKSa]

I'm not trying to be argumentative, I just want to be able to understand the reasing behind someone that thinks changing their springs after as few as 500 rds.

I think that replacing a spring every 500 rounds would be an extreme case. I can't imagine that would make any sense at all unless we're talking about a very small/light pistol in a substantial caliber.

I don't understand the difference between the work an AK, SKS, AR, FAL recoil/buffer spring does in cycling after each round and the work that a pistol does doing the same thing.

One spring is simply returning the bolt after an extraction/ejection cycle while the other is actually absorbing recoil energy.

The bolt return spring is being propelled backward by a calibrated amount of force determined to be sufficient to extract/eject the emptry cartridge and controlled by the size/position of the gas port. A recoil spring must absorb the recoil energy generated by firing the cartridge. That may be far greater than what is actually required to merely extract and eject the empty cartridge.

There's a slow motion video of an AK being fired full-auto with the top cover removed. You can see that the bolt is only bottoming out occasionally, and even in those cases it's not hitting the stops with a lot of energy. Compare that with a recoil spring which bottoms out (is essentially fully compressed) for every firing cycle.

If a gun requires a spring pressure of 15-30 pounds to operate properly, I thin any good engineer will design enough of a margin for error to allow the 25# factory spring to be well over the minimum strength after a 20% decrease in strength due to a weakened spring.

The problem is you don't just get to pick a recoil spring weight that's as heavy as you want or you might end up with a slide that can't be operated by people with typical hand strength.

A designer is caught between conflicting design requirements when working with very small recoil operated pistols. The slide can't be too hard to work and yet the recoil spring is called upon to do extra duty. In that situation it makes sense that a recoil spring might require much more frequent replacement than in a full-sized pistol of the same caliber.

[OJ]

I dunno about all those other spring problem but, I strongly suspect the firing pin spring that allowed the firing pin stop to drop down and block the slide from going into battery and I have something in common - we're both old and not as strong as we once were -

[Walt Sherrill]

This is the right answer right here. I'll make one addition. People need to stop thinking of this as "past the elastic limit" issue.

The greater % of compression as compared to the length of the spring in its natural state... the quicker it fatigues. As mentioned above, this is not a linear rate.

It may be terminology that's messing with our heads, again -- and how we laymen interpret those words.

It could be that a spring's "elastic limit" (optimal operating range) varies depending on what the spring is intended to do. In some cases it might be the 25%/1:4 figure you cite (for aircraft, for example), but in others, something different. In some cases, that "elastic limit" may included planned degradation -- a shorter life, because that's what's required for the gun to operate properly. That's not "planned obsolescence" to sell more springs, but an attempt to do what the gun designer needs the spring to do for a properly functioning gun. I've never noticed that a Wolff spring performed less well than a factory spring. (I will note, too, that many gun makers, who sell springs, simply repackage Woff Springs under their own label.)

It could be that aircraft springs, as in landing gear, are intended to have a much longer service life and are designed to not compress too much to keep maintenance costs down. Replacing a major spring in an aircraft's landing gear is arguably a major maintenance task, requiring down time with the aircraft out of service. Replacing a recoil spring is a much less arduous task, with fewer economic costs.

As JohnKSa notes, above, most recoil springs are almost FULLY compressed during their work cycle, and many high-cap mag springs are also equally jammed into a relatively small area. For these springs, the amount of compression is far past the optimal 25% compression rate cited by the aircraft expert, above. A mag spring that is maybe 10" long in it's coiled form (but made with maybe 15"-30" of material in those coils) can be squeezed down to 1"-1.5" or less, in a high-cap mag. The same sort of thing happens with springs used in sub-compact gun mags.

In my CZs, the 10-round mags use the same springs as the 16-round mags; which spring is likely to have a longer life, do you think? The 10-rounder is lifting less weight and being compressed less with each mag reload though it may fire the same number of rounds over time.

I guess we need to understand what Wolff means by "elastic limit" before we discount the term. It may be a "term of art" that means something different to an engineer in the spring business than a layman on a gun forum. I may drop them an email and see if they'll explain.

I'm also beginning to wonder whether Coil springs are fundamentally different than leaf spring in how load is distributed and wear is manifested. Maybe springs aren't springs, after all -- and maybe coil springs just "wear out" DIFFERENTLY than leaf springs. But, I DO suspect that metal is metal -- which maybe is what Bill D's claim that "springs are springs" really means -- that the material will break or wear in predictable ways if we just know what we're looking for.

.