In S&W revolvers J frames has main coil springs meanwhile K, L and N frames has main leaf springs.

Others brands like Ruger or the Colt Mark III and Mark V has main coils springs.

I like more the feeling of the trigger of the K, L and N frames S&W, but in this opportunity I want to ask about endurance or resistance. Which one does have more endurance or resistance to abuse? The coil springs or the leaf springs?

Smith's are trouble free for the most part,and last for decades that way.

Also you have just touched the reason I prefer I-frames to J-frames for small guns... they have leaf-type mainsprings and are just like little bitty K-frames. I'm not sure what made S&W engineers switch to coil mainsprings in the '50s for the development of the J-frame, since the leaf springs had been working well at that time for well over 60 years.

Froggie

Ruger has always insisted that its coil springs are more durable. You could not prove it by me. I have never had one break during shooting or handling such as dry firing, and that includes revolvers made as far back as the 1920s. I have friends who have fired revolvers older than that without ill-effect.

I believe coil springs are the more durable of the two.
Leaf springs last forever, but I have seen them break.
I have never seen nor heard of a coil mainspring breaking.
Must say I like the flat main spring feel a little bit more, though.

As an engineering professor - teaching mechanical engineering design - if the two types of springs are designed properly, there should be no difference in their reliability. Whether that is actually done will determine which will fail first, if either.
We try to teach all of our engineers equally, but some make "A's" some make "B's". some make "C's", etc.
The "quality" of a spring will depend more on which engineer designed it, not the type of spring.

All else being equal, the one designed with the most reserve (overdesigned?) will last longer, but it is NOT all equal in gun design and size. I've had to replace two J frame coil main springs in loaner .22s to solve failure to fire after many tens of thousands of rounds.
Recoil springs have made a greater impression on me, because the flat-wound recoil springs are superior to the piano wire springs, and last a year in competition no matter how many rounds.
I've been suckered into buying some cheap aftermarket magazines whose soft springs were good for maybe ONE DAY of practice.

Would not expect it to break, just go weak from use and need replacing.

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Science plus Art

I have S&W's from every decade from 1860 to present, and have yet to ever replace a mainspring for failure to function, even my 1899 1st Model M&P. I bought a parts box at an auction awhile back and there are about a dozen mainsprings (flat) in it as well as maybe a dozen coil J Frame springs. They are all original equipment, assuming whoever they belonged to originally replaced them with lower powered aftermarket springs. I have fixed a couple revolvers for friends that someone did a "trigger job" on ruined a mainspring. (You just can't bend a flat mainspring and get reliability out if it.)

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H Richard
SWCA1967 SWHF244

"Would not expect it to break, just go weak from use and need replacing."
Can you explain exactly how springs "just go weak from use"? I have always heard that, but since there are no time-dependent terms in the equations for spring design (static stress and strain) I have wondered how that could be.
(Not talking here about fatigue-failure - a totally different situation.)

rjb1: I have never had a problem with S&W springs, coil or leaf, but when I was doing some part time gunsmithing in the 1980's and 90's, Remington 3200 O/U shotguns were popular for skeet and trap shooting. I had to replace a lot of original springs that developed a tendency to miss fire. The 3200 used very light hammers and very strong coil springs in an effort to get a fast lock time. When comparing the replacement springs to an original used spring, there would be about 1/8" difference in length, with the old, miss firing springs being shorter. I always attributed the problem to the original spring not being properly heat treated, thus allowing it to "take a set". The problem was apparently identified and solved, because I never had to replace one of the new springs.

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Tom
1560

There is a mindset out there now that gun springs need to be regularly replaced. I do not know where this came from. As far as I know, every gun I own has its original springs, and they work.

You have now, had a coil spring break in a Python. (bolt spring) I thought it was pretty odd as well, it did have way over 100K rounds through it from me and I bought it used, but still - mfg defect from the start perhaps? I too prefer the feel of the flat spring better.

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K & N S&W revolvers

I prefer the feeling in the trigger of the S&W K, L and N frame more than others.
But my question was because the other day I was doing dry fire with my model 10-5 and snap caps, at the end I was coking and un-coking the hammer when I heard a click and the hammer lose tension. I remove the grips and noticed the leaf spring was broken in two parts.

The equation does not have a term for it because it is an engineering equation, not a complete description of the physical process. That does not change the fact that even well made and designed springs change with repeated flexing. We're talking physics now, not engineering, so we can't ignore actual physical processes to get a neat formula for designing. I'm a physicist, but I took several engineering courses at UW.

Take a valve spring from an internal combustion engine that has run 200,000 miles, test it, and unlikely it will pass spec for a new spring. Maybe not so important for an old work truck that never gets over 4000 RPM. However, race cars turning 9000 RPM get frequent spring changes, since their springs work more at the limits of performance and a weak spring can float a valve at speed.

Lighter springs in a mechanism, such as a firearm, puts it nearer the limits of performance, so it is common practice for top competitors in USPSA and IDPA to discard all the springs at the annual teardown of the competition gun. As an aside, a fellow shooter from OK broke a coil mainspring the last match of the season (GA Championships). The round count for the year was just over 63,000. Coil springs rarely break, but they can.

Several have commented that stock springs in firearms very rarely break, and I can attest to that from matches. Aftermarket lighter springs break more often than stock.

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Science plus Art

"That does not change the fact that even well made and designed springs change with repeated flexing."
You are bringing in fatigue failure here - which I was specifically excluding. *Very* different principles apply...
We are talking about STATIC failure (or permanent deflection) here. Put in the shooting vernacular, "the springs get "tired" if left compressed for some extended time period". We all probably know people who think they need to change their magazine springs every year or six months to prevent the springs taking a permanent set ("getting tired") or that you should not leave a gun cocked to "preserve" the mainspring.
That particular shooting urban-legend is what I'm talking about.
Here's how springs are designed (as normally done):
STATIC Failure:
1) Choose material - can be relatively high-carbon steel or an alloy. Not counting corrosion, the ingredients of the material will not change with time, so that is not the explanation for the "getting tired" effect, if it exists.
2) Choose physical dimensions: This can be L x W X H for leaf springs or wire diameter and coil diameter for coil springs. In either case, not counting for wear (which doesn't happen in the static case), there is no change in geometry with time, so that is not the explanation for the "getting tired" effect, if it exists.
3) Stress Evaluation and Spring Constant: This step is done in conjunction with Step 2, in that the amount of force required for the spring's operation and the equivalent deflection are related to the physical dimensions. Once the proper decisions (and calculations) are made, you can expect the spring to exert sufficient force to do the required task (feeding-rounds, for example), without exceeding the allowable stress in the spring material.
If the internal stress exceeds the yield strength, the spring will take a permanent set, and if it doesn't, it won't. If the yield strength is exceeded, due to poor design, it will happen the *first time* the spring is deflected and the time duration of the applied force has nothing to do with it.
Leaving rounds in a magazine or leaving a hammer cocked will not have an adverse effect as long as the spring is designed properly. As stated, even if it is NOT designed properly it still doesn't affect the lack of time- dependency involved in permanent deflection (or failure) - it would fail at the first application of force, not experience a failure at some distant time in the future.

Difference in STATIC failure (deflection-stresses only) and FATIGUE failure (repeated stress) and related analysis:
The STATIC strength and FATIGUE strength are related in some ways, but are definitely not equivalent either in theory or practice.
You could write a book on fatigue failure analysis, and many people have. Among other interesting aspects is that you can sometimes remove material from an object, thus raising the average stress (STATIC case), while at the same time significantly improving the fatigue life of the part (number of successful cycles).
Fatigue design/analysis also has an aspect of art, as opposed to science/mathematics, as OKFC05 implied ("...not a complete description of the physical process").
As my favorite machine-design text states, "It is very important for the designer to develop a "feel" for stress concentration so that he will know intuitively when it exists and what to do about it."

This goes back to my original contention that the quality of the design-engineer is at least as important as the specific type of spring (and related systems).

Yes, it seems to me that fatigue is central to the issue the OP raised:
Sitting in a static load seems outside the realm of abuse. As you noted, only a grossly inadequate spring would fail sitting stationary subject only to its designed static load.

Thanks for the interesting follow-up post. It brought back memories of the time I spent doing reliability tests for Air Force systems, and the really oddball failures due to transients and harmonics. When people ask me about the "tampax in the trigger spring of M&Ps" I tell them its magic, and the spring will break if you take it out.........OK, so it's a damper to prevent harmonic concentration of dynamic stress.

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Science plus Art

Professor,

I've always assumed S&Ws have a more consistent DA pull thanks to the leafe spring, whereas coil spring guns always seem to get heavier at the end, at least the ones I've tried including a Colt Trooper MKV, two Ruger Security Sixes and a Redhawk. I've drawn the conclusion that coil springs will always stack as they're compressed. I don't know if "stack" is an engineering term, but that's generally what it's referred to, in revolvers and bows. I've dabbled in building traditional long bows just enough to know that given equal draw length/weight, a shorter bow (straight limbed only) increases stack.

Can you confirm this?

I do know even leaf springs will stack. I assume that's due to design.

Great thread!

I´m sorry my English is not good enough, what does Tampax mean?

I'll let OKFC05 explain "tampax" and then I'll get back in the discussion. (insert smiley-face here)

Compressed fiber inserts (a.k.a. "tampax") inside coil springs dampen spring vibration and harmonics. I presume this makes the spring last longer, particularly at the point of attachment, where vibrations can cause added wear between component(s) and the attached spring end.

This Sigma trigger return spring has an insert, for example......

https://www.gunpartscorp.com/Products/343240.htm

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Ret. LE, FA Instr, S&W Armorer

Thanks a lot for the explanation.

I prefer the leaf spring of a K, L, or N frame.

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What would Jim Cirillo do?

Some of us old trap shooters have debated this for years Even in "high-end" competition shot-guns, you'll see both kinds. As an example, Ljutic and Krieghoff use coil springs, while Perazzi uses leaf, and Beretta uses coil in some and leaf in others. The best explanation I've heard is it depends on the geometry of the design ( as in side lock vs box lock--but then Perazzi is a box lock-go figure ), as in the difference in a S&W vs Ruger revolver ?

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John

My K frames and L frame have actions that my J and Improved I frames can only wish for.

Which one will last longer? I don't shoot them enough to worry about it.

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What would Jim Cirillo do?

The definition of the word "Tampax" is what was asked for and we may be embarrassed to say exactly what it is.
"Tampax" is the brand name for feminine-hygiene products used during menstruation. I think "tampon" is the more generic name for the product.
With that in mind, look at the location of the white material inside the spring coils (on the link) and you'll see the analogy.

Enough biology, I'm an engineer, and I'll stick to that from now on.

As OKFC05 said, the material inside the spring is called a "damper" and does absorb (and then dissipate) energy. Dampers of various sorts are essential parts of a properly-designed dynamic system.
Designing for proper dynamic behavior of any system is both interesting and challenging. As OKFC05 says, "there are all sorts of really oddball failures due to transients and harmonics."
Perhaps the most famous of those is the failure of the Tacoma Narrows Bridge in 1940.

Watch the Youtube video and you can see that the wind isn't strong enough to blow a guy's hat off, but it's enough to cause the bridge to fail catastrophically. (This is due to a phenomenon known as "vortex shedding" at the structure's resonant frequency. This is due to the interactions of both fluid dynamics and structural dynamics, but it illustrates the importance of considering the dynamic issues in designing anything, including firearms, which is the topic of interest.)
These questions/issues are mid- to upper- level mechanical engineering topics (with some grad school thrown in).
It's the weekend, so class will resume on Monday, for those interested in looking at some of the details involved in these matters.
(OKCF05 feel free to join in, since you also have had practical experience in this stuff...)

I have found many leaf springs weak and taking on the arch that the preload has set upon it through the years - let alone the continual working of the action on a shooter.

I have also found MANY J frame guns exhibiting "coil bind" due to too long of a coil spring. This causes the last bit of hammer pull to be extremely difficult as you are "crushing" the coils together. That seems to be an engineering problem. I have fixed many by simply cutting the coil a bit shorter.

There is no doubt that the leaf spring provides the smoother action.

Who has ever bragged about the incredible smooth action on their J frame?

Looks like we are right back where we started.

I never had tried an old I frame with a leaf main spring, how good (or how bad) was the action of those olds I frames?

Once somebody told me the J frames needs a heavier main spring because the hammer of the J frames are lighter and needs that strength to ensure the firing pin hits the primer with enough authority to detonate it.

Beside the hammer are light, the J frames has less leaver effect due its small size parts. And that is another reason because it needs a heavier main spring.

Forgive my bad English.

There is at least one PPC gunsmith, Travis Strahan, who will put a coil spring in a K or L frame. A friend likes his.

MY Perazzi MT6 had coil springs, although in the minority for that make. Sorry I sold it.
It is not a boxlock in the usual Anson and Deely sense; it is a trigger plate action akin to Dickson, MacNaughton, and Brown "round actions" and the German Blitz, but rendered quick detachable.

Señor Barca, there is nothing to forgive about your English... it is better than much of what is posted here regularly. Sorry I can't find the proper letter n on my keyboard to write "señor!" Oops, there it is!

As for your question about the original I-frame guns with leaf mainsprings like their larger siblings, I find them to be smoother than the later coil spring guns; it's difficult to describe and it may be somewhat imagined on my part, but I definitely think it is there. I'm not sure that the reduction in size changes the geometry of the hammer sufficiently to produce the difficulties with ignition you mention, and to be honest I've never had a misfire with any of my several I-frame guns that could be blamed on that factor.

Of course another thing to consider is that all of the I-frame guns were made at least 60 years ago and most have been "worn in" to the point of being smooth, but I just don't think a well worn J-frame comes to the same level of trigger pull (even though I have a Baby Chief that comes pretty close!) I've even considered converting a Model 36 to leaf spring, but "considered" is as far as I have gotten.

That's my personal and probably biased opinion on the subject, or as we say around here, "That's my story and I'm sticking to it!"

Froggie

Mr. Green Frog, thanks a lot for sharing your experience. I had always wondering how was the trigger feeling of those I frames with leaf main spring.

Maybe the reason that some people (me included) tends to believe that the coil main spring is stronger is for the the Single Action Army 1873 type case, The Colt Single Actions Army has leaf main spring and the Rugers Single Actions has coil main springs, and the colt mains springs broke more often than Rugers.

Maybe in the double action K, L and N frames are different.

It is pretty widely accepted that a coil spring is more durable than a leaf spring, but that is not what my main concern would be... I want the trigger pull to be great while still having the ability to set off primers dependably. If I have to change out a leaf spring from time to time, so be it, but so far none has ever broken. Other folks' mileage may vary. At this point I haven't been able to bring myself to convert a Model 60 to a leaf spring, but I haven't totally abandoned the idea either.

Froggie