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Spring Fatigue Made Easy

Finally, The Answer About Does It Hurt Mag Springs To Keep Them Loaded

In this article I hope to clear up some terms, beliefs, share some opinions about spring wear, spring fatigue, spring set, and spring lifespan and I hope to make this topic as clear as mud. However, after you read this, you will know more about springs than 99 percent of all gun owners.

This topic usually boils down to about three opinions. One, don"t worry about it. Two, rotate and change your loaded mags. Third, don"t fully load your mags leave one or two rounds short.

Like many subjects in life the right answer is normally, "It Depends."

If you own guns, springs are part of every gun. Every time a gun shoots you use anywhere from one to six or more springs. Surprisingly there is not a lot of clear information about spring use, abuse, cleaning, wear or failure. (A Glock pistol has six)

When it comes to this topic you will normally find two types of people, the worry warts with more money than sense that want to replace springs every six months, and the I don"t care since I heard from a friend that a gun was found from WWII loaded for 30 years and it fired and worked fine.

So which is it? Well I think the truth lies somewhere in between. I would hope after you read this article that you will, at least, have a better understanding of springs, so you can make your own educated decision.

Let"s start with what a spring is. A spring is an elastic object used to store mechanical energy. That energy is stored and released. When a spring is said to be neutral or set, it has neither stored nor released energy, per say.

* Springs can get worn out, but more by neglect and using them not for their intended use.

Springs come in three main types and guns use all three. The most common types of springs are Compression (Coiled), Torsion (twisting) and Tension (extension).

Coiled springs appeared in about the 15th Century in door locks and spring powered clocks. Coiled springs is what you have in your guns like your buffer spring, magazines, recoil spring and extract/ejector springs. Coil springs work when they are compressed from its resting position and that energy is released when it is decompressed. The spring exerts an opposing force approximately proportional to its change in length. So when it is not compressed there is no stored energy to release. Compression springs can be prone to buckling, which is why some use guide rods or small enclosed areas that support the spring, to prevent buckling.

Torsion spring is a spring that works by twisting. Torsion springs give energy when torqued or twisted. When it is twisted it has stored energy that can be released. In guns, these springs are most commonly found in the Trigger or slide lock/release.

Tension or extension springs tend to pull things back to position. A tension spring is a helical cylindrical spring with approximate constant stiffness which is able to receive external forces acting away from each other, on its axis.

The Difference Between Conventional and Variable Springs:

The difference is both physical and operational. With a conventional spring, all the coils are spaced equally apart, except for the closed ends. In a variable recoil spring the space varies between coils with less space between coils at one end and more space between coils at the other end.

The way the two springs store energy is also different. For example if a conventional recoil spring is compressed 1/2", it might store 1 pound of energy. For every additional 1/2" this spring is compressed it would then store 1 additional pound of energy. When a variable recoil spring is compressed 1/2", it might store 1/4 pound of energy. The next half inch of compression might store 1/2 pound, the next half inch might store 3/4 pound and so on. In other words, a conventional spring stores energy on a straight line and a variable spring stores energy on a curve. If both springs are rated at 16 pounds, they will both store 16 pounds when compressed to the same working length, but the way they get to 16 pounds is different. (unknown source)

Now we that we know the types of springs, let"s take a look at the different materials used in making springs.

Music Wire:

This is a general term referring to a range of high carbon steel wires. The term "music wire" is used because guitar and piano strings are typically made from this type of material. It is the most common material for small springs.

Chrome Vanadium:

This is an alloy steel. It has small amounts of both chromium and vanadium added to it to allow it to withstand higher operating temperatures. This material can be plated.

Chrome Silicon:

Another alloy spring steel with typically just over 1 percent silicon added to increase heat tolerance. This material can be plated with proper techniques.

17-7 PH Stainless Steel:

This is a high strength cold drawn and precipitation hardened stainless steel. This material typically has a blue to brown color after heat treating. It has general-purpose corrosion resistance. It is magnetic in spring temper.

- Springs can be made from hardened steel or can be hardened afterwards depending on the process

Many think the best spring materials are chrome silicon (CS) alloy and 17-7 PH (mil-spec stainless steel). CS springs will endure 500,000 cycles with single-digit performance loss percentage. CS can also be heat-treated (also called hardening or tempering) and shot-peened after forming to enhance spring-to-spring consistency and better performance. CS also endures heat up to 750 degrees Fahrenheit with no changes, however music wire can diminished at about 175 degrees Fahrenheit. So obviously, where the spring is being use will dictate how much heat it will be exposed to.

Most common spring materials generally fall within each other to a 10 percent window of strength. So the fatigue limit (lifespan or failure point) of the various materials, doesn"t really vary that much, under most conditions. Physical design factors such as wire thickness, number of coils, surface finish and care of the spring have a larger impact on the life of the spring more than anything else.

All materials have their advantages and disadvantages, so many considerations go into play when designing springs for specific intended uses. So when gun manufacturers pay engineers to design, test and develop springs, they probably know what they doing in order to prevent failures, accidents and lawsuits.

What Causes A Spring to Fail:

This seems to be where most people part. My philosophy, in the past, has always been, why keep a spring under tension when you don"t have to? I am a little old school and was programmed with information from the Vietnam era, when the M16 was first used and had many failure problems that got people killed, so that is where that belief comes from. However, with the advancement of materials, education, coating and standards, I have come to change my position.

By definition, a static load (e.g., a once-loaded mag stored indefinitely) can never produce fatigue failure. You need a cyclic load (e.g., a repeatedly loaded and unloaded mag).

Springs fail from various causes. Some of these are improper uses, lack of care and neglect, metal fatigue, corrosion, damage, extreme hot or cold or small percentage of production failure.

Fatigue or metal fatigue, is the failure of a component as a result of cyclic stress. The failure occurs in three phases: crack initiation, crack propagation and catastrophic overload failure (lack of care and rust increase the chances of all three). Fatigue failures often result from applied stress levels significantly below those necessary to cause static failure. An example of static failure would be a fully loaded magazine just sitting there, the spring is dirty, rusts, weakens and then the spring breaks. Very rare and I have never known this to happen. Cyclic stress is compressing AND stretching of the spring which puts more wear on a spring than just sitting, both with no load (unloaded) and under load (loaded). However, mag springs are designed and engineered to be loaded and unloaded, so using them does not damage the spring. If you are over loading them or taking the mag apart and stretching the spring out, then you are not using them, in a way that they were NOT intended or designed.

Fatigue may be the wrong word. When a spring is cycled many, many times it can crack from metal fatigue. Most modern springs generally will go from 100,000 to 10,000,000 flexes before failure due to fatigue (unknown source). Remember, extreme cold or heat will also effect spring performance and fatigue.

Spring fatigue happens when you repeatedly compress and release a spring. Over time, the "cycling" of the spring from a compressed state to a relatively uncompressed state will weaken the spring in area where there may be tiny imperfections in the metal. How quickly this may happen depends on the type of metal used, the conditions of use and the frequency of cycles. Engineers define metal fatigue as weakening or failure resulting from cyclic loading (loading / unloading). A static load (not moving) does not cause fatigue.

The greatest danger to guns springs is corrosion. Springs are typically the thinnest metal in a firearms which make them extremely vulnerable to catastrophic failure from corrosion. Design parameters allow for this which is why stainless steel seems to be a popular choice for firearm springs.

Spring Set:

Manufacturers plan for and work "spring set" into the design of springs. Springs can and will get what is called "spring set". Basically this is when a spring is put under load for the first time, it will shorten and lose some of its length and range of motion. Spring set can work both ways, when pulled in opposite directions or when compressed. Spring set is not the same as spring fatigue, unless you are over compressing or stretching. Older springs, probably before 1940 or so, are more likely to take a "set" if left compressed than newer springs made today.

Metal fatigue is generally a term used to attribute failure to metals - work hardening, crystallization - failure due to inclusions, voids, poor heat treatment etc. A spring works thru torsion - a spring that is brand new when left compressed will almost inevitably take a small, but measurable ""set"". Once that has occurred the life of the spring will be longer than most things they are in and longer than you will be around.

Spring set is normal and is not a concern and should not be corrected. I.E. Attempting to stretch the spring to make it longer. Modern day springs are heat treated and tempered which means they would return to length even after 10 years of compression.

What is Creep:

Creep is a slow degradation in the strength of a metal used in a spring such that over time it loses its elastic capabilities. Spring creep is usually a concern under extreme conditions. Creep normally doesn"t occur at room temperature. As a rule of thumb, creep processes occur at about melting temperature. When the spring is compressed or expanded beyond its normal range, usually causing heat, creep can happen. Compressing a spring and stretching it beyond what it was designed to handle, will indeed, cause the spring to deform.

Shot Peening:

Shot peening is a cold work process used to finish metal parts to prevent fatigue and stress corrosion failures and prolong product life for the part.

Hardening and Tempering:

Metal hardening processes is a way of making steel harder. By first heating the steel and then quickly cooling (quenching) it, the steel will become much harder, but also more brittle. Steel can be treated by intense heat to give it different properties of hardness and softness. This depends on the amount of carbon in the steel (only high carbon steel can be hardened and tempered).

Tempering is a low temperature (150 C to 650 C) heat treatment intended to remove the stresses and brittleness caused by quenching and to develop the required mechanical properties.

Some Science Behind Springs:

Young"s modulus: Young"s modulus, also known as the elastic modulus, is a measure of the stiffness of a solid material. It is a mechanical property of linear elastic solid materials. It defines the relationship between stress (force per unit area) and strain (proportional deformation) in a material.

Material stiffness should not be confused with strength, hardness or toughness.

Strength: the strength of material is the amount of force it can withstand and still recover its original shape;

Geometric stiffness : the geometric stiffness depends on shape, e.g. the stiffness of an I beam is much higher than that of a round tube made of the same steel, thus having the same rigidity, and same mass of material per length.

Hardness: the hardness of a material defines the relative resistance that its surface imposes against the penetration of a harder body.

Toughness: toughness is the amount of energy that a material can absorb before fracturing.

As long as they are not stretched or compressed beyond their elastic limit, most springs obey Hooke"s law,

Hooke"s law is a principle of physics that states that the force F needed to extend or compress a spring by some distance X is proportional to that distance. That is: F = kX, where k is a constant factor characteristic of the spring: its stiffness, and X is small compared to the total possible deformation of the spring. (This just gave me a headache)

The Modulus of Elasticity (also known as the elastic modulus, the tensile modulus, or Young"s modulus) is a number that measures an object or substance"s resistance to being deformed elastically (i.e., non-permanently) when a force is applied to it.

Some Not So Scientific Evidence:

A paperclip is like a spring, it holds it"s shape, but if you bend it out of its set shape or bend it back and forth several times, it will heat up and break. Springs are made of much better materials and processes but the same is true. If you bend them out of shape, use them for other than their intended purpose or expose them to extremes heat, abuse or use, they can fail. However, with normal intended use and proper cleaning and care, good quality springs are pretty reliable and not likely to fail in your lifetime.

One man said, I have a gun, which turns 100 in two years. Works great. Incidentally, one of the selling points of that shotgun was that the springs were guaranteed never to take a set. I have a letter from Ithaca to my grandfather, dated 1949 reaffirming that guarantee on the springs. They said never and they meant it. Ithaca is gone, but those springs are still fine. (*note: if they were making springs that good in 49, should you really worry about springs made today)

Another man said, How many of you have ever made a spring? I have probably made more springs than everyone reading this article, combined. Modern springs may take a slight set the first time it is compressed. After that it should work indefinitely. Signed: Bill DeShivs, Master Cutler

And another man makes this point, Tomorrow I"ll drive a car to see my family. For the engine, that"ll mean five hours at a minimum of 2000 rpm. Each valve spring will be compressed every second revolution, or 5 x 60 x 2000 / 2 = 300,000 times. Roughly a thousand times per mile. So far the valve springs in my car have been compressed and released about a hundred million times. Last time I checked changing valve springs is not on the inspection list. They"ll be good for another one or two hundred million compressions. And there are people worrying about magazine springs that will be a compressed and released a few hundred or thousand times at the most. (this is a pretty good point)

And I say, in 30 plus years of military and police work, working with guns my entire life, I have never seen, heard of, or known anyone that has had a spring fail in a gun. Now I have had to replace a few springs from being modified, cut, filed, bent, stretched, put in wrong and rusty, but never a spring used normally and cared for. At they go over springs design and tensions testing, it appears their standard for spring testing and failure is 10 to 5th power, (100,000), so it is reasonable to believe that most springs will last 10s of 1000s of times under normal usage, much more than anyone will ever load and empty a magazine. In the big picture, I don"t think a lot of time should be spent worrying about springs, other than cleaning.

Some Suspicious Recommendations From Spring Sellers:

This is an excerpt from a Lucky gunner article:

How often is "periodically"? That"s a great question. A gunsmith at Beretta (who claimed not to be speaking on behalf of the company) told us he rotates his personal carry magazines every two weeks.

The customer service rep we spoke to from Sig said that once every six months would be sufficient.

However David Cochol of Mec-Gar, the company that manufactures the factory magazines for Sig (as well as Ruger, S&W, CZ, and several others), gave us the answer that seemed most common; "We recommend following standard law enforcement practice and that"s to rotate magazines every 90 days." He also suggested that rotation as a good opportunity to field strip, clean, and inspect the magazines to make sure there aren"t any other problems that could cause malfunctions.

My response to this, I have never heard of any law enforcement agency rotating mags or for that matter taking apart mags and cleaning them. So not sure where the hell they got that from. However, I always say don"t ask a Barbara if you need a haircut and don"t ask horseshoer if your horse needs shoes. When you ask someone that sells something if you need one, they will always tell you YES. So when a spring manufacturer, Wolff Gun springs, tells you that you need to replace springs every six months, I call horse pucky. If you are making springs that are so crappy they need replacing every six months, perhaps I should not be using your springs.

Miscellaneous Stuff and Common Sense Factor:

Many people say loading and unloading does damage to mag springs. Magazines are made for loading and shooting (unloading them). That is their intended use.

If you have a mag issue and think it is a spring, mark that mag with "T" for training mag and use it at the range to help you practice failure drills and tap and rack drills.

New mags are always hard to load, over time they load easier. This is normal and should not be a concern. This is not spring failure and may be a little bit of spring set.

Dirt, lack of care, rust and neglected springs will deteriorate springs more quickly than use.

Magazine maintenance is the difference between have an expensive single shot or a working semi auto.

Springs are made to work within the range that they were designed for, use them that way.

Fully loaded mags can be hard to seat in a weapon from too much pressure, normally created by someone trying to squeeze one extra round and force it into the mag. That little bit of play after a mag is fully loaded is there intentionally so the mag will load under pressure.

A two dollar magazine will not have the same spring as a 15 dollar magazine.

Needless administrative handling breeds complacency and should be avoided. (Safety Sallies)

A 30 round mag is designed to hold 30 rounds, loading it with 29 rounds makes it a 29 round mag, to my knowledge, they do not make, design or manufacture 29 round mags.

In Conclusion:

Will you ruin a mag spring by keeping it fully loaded? Are springs really a valid concern if they are cared for and used for their intended uses? Do springs really need replacing every six months? These are questions that you have to answer for yourself. I hope this information helps you in making your own informed decision.

For me, spring failure and spring concern is in the category of I don"t worry about it too much.

Some Links and Reference Sites On Springs:

Site about spring designs:

Site with a spring specs calculator:

Site about springs:

Site about Spring Failure and other Spring information:

Site about types of spring material:

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