1911Forum banner

The myth of the chrome-silicon gun spring ‘not taking a set.’

28K views 39 replies 29 participants last post by  log man 
#1 ·
It is NOT true that chrome silicon magazine springs are more resistant to taking a set than all stainless steel or music wire. I wish I could say that I am surprised this false marketing claim took hold, but sadly in the past I believed it as well. That is, until I researched it.

Springs have a characteristic called the proportional limit. When you compress a spring, you add stress. When the spring deforms, that is strain. Normally there is a proportional ratio between stress and strain. If you continue to deform the spring past a certain point, this ratio is no longer proportional and you have reached the limit for taking a permanent deformation (set). For three types of springs commonly used in guns, Music Wire (ASTM A228), Chrome-Silicon Valve Spring Quality (ASTM A877), and 17-7 PH stainless - the stress limit is 45% of the minimum tensile strength on the material certification.

For music wire, the range of the tensile strength property is 230-399 KSI. For chrome silicon, it is 235-300 KSI. For 17-7 PH, it is 235-335 KSI.

http://www.tribology-abc.com/calculators/properties_of_common_spring_materials.pdf

One cannot make a general statement about any of these materials without knowing the exact tensile strength of the specific material the spring maker used. You can see they have overlapping strengths, so without further information, they can be considered about the same.

One brand may make a better choice on post-winding stress relieving, or some post-processing such as shot peening, but one thing is clear – the BEST music wire is stronger than the BEST chrome-silicon. This is because with the higher tensile strength, 45% of that will be a higher stress value that one can impart before there is disproportionate strain resulting in a permanent set. Music wire wins the ‘resistance from set’ argument.

So why does chrome silicon exist? Music wire is limited to 250 degrees F. In a car engine, the temperature exceeds that. Chrome silicon wire is used for valve springs for this reason. It is more resistant to taking a set AT TEMPS ABOVE 250 degrees. Needless to say, firearm magazine springs do not reach this temperature and recoil springs likely never will either (AR extractor springs may). And if you want to go above the 475 degree F limit of chrome silicon, there are stainless alloys. They cost more, but have similarly high proportional limits as chrome silicon.

There is also an issue of fatigue strength. This is the ability to resist damage that occurs from cycle loading. Cycles are often measured in thousands or millions, and are not that important for magazine springs. They are important for recoil springs. Does chrome silicon wire outperform music wire for fatigue strength? No, it is worse. Music wire has a cleaner surface – and surface defects can reduce fatigue strength.

http://tinyurl.com/c9hdqu

“Music Wire:
Due to superior surface quality, these can withstand higher stresses under repeated loading than any other spring material.”

http://www.centuryspring.com/pdfs/techfaqs.pdf

“14. What are the best materials for fatigue applications?

The two most popular materials for fatigue applications today are Music Wire (ASTM A228) and Chrome-Silicon Valve Spring Quality (ASTM A877). At wire sizes below approximately 0.080" (2.0 mm), Music Wire offers higher tensile strength; however, Music Wire’s maximum service temperature is less than that of Chrome-Silicon.

… processing of music wire is done in a manner to provide a finished surface with smaller allowed defects than hard drawn wire. Since surface defects are one of the most common initiation sites for fatigue cracks in springs, smaller surface defects (and their corresponding reduction in stress concentration) enable music wire to be used in high cycle fatigue applications.”

The way one designs a spring to not take a set is to physically not allow it to deform in a way where the stress exceeds the proportional limit. This may mean designing a pistol magazine to only take 12 rounds rather than 13, or add more coils to the spring, or use thicker wire, or use flat wire, or increase the OD. A properly designed system will allow for a fully loaded magazine to sit for over 100 years, or for an action to remain locked open without the recoil spring taking a set. Are some platform magazines improperly designed? Most certainly, but no one has seems to identify which ones.

What about tests that prove chrome silicon gun springs take less of a set than music wire or stainless steel? I have seen a few tests and they prove no such thing. They are often done with different wire diameters, free lengths, number of coils, shot peening, stress relieving, and heat treatment. It is impossible to know if each spring was properly made. One does not need to do a test to know which alloy has a higher proportional limit as that is well known and defined in engineering texts. However, one can do tests to show if a specific brand spring is better than another specific brand spring but it would NOT be just because they replaced stainless or music wire with chrome silicon. So search for a quality spring, but don’t go by alloy alone.

So what is the ultimate magazine-spring material? Since all three have similar resistance to taking a set given the same wireform, one needs to look at cost, corrosion resistance, and temperature resistance. Temp resistance is not a factor and fatigue life is usually not either. Corrosion resistance is a strong factor. Cost is a factor for large production but not individual enthusiasts. 17-7 PH seems to win.

What is the ultimate recoil spring? Again all three have three have similar resistance to taking a set given the same wireform, In some applications, the 250 degree F limit of music wire is not an issue (handguns). In some (belt feds), it may be. If a pistol design allows for enough room to have a wireform where the ratio of stress to tensile strength stays low, then one may go with 17-4 PH to pick up corrosion resistance. If the design, as is true with a 1911, is one of high stress and yet temp is not a factor, then music wire seems to be best (I believe this is what Wolff uses). If the application is such where temps may get over 250 degrees F (either through combustion or simply through spring cycling) and there are high stress and fatigue considerations, such as an AR15 extractor spring, then chrome silicon would seem best. And if the temp gets really hot, such as in a gas block part, then 17-7 would be good.

For any spring, proper heat treat / stress relief and shot peening will increase the limits.

When you see a gun spring company claim chrome silicon is 1000 times more resistant to taking a set than music wire or stainless (yes I have seen this claim), you should ask them to prove it. They can’t, because it is not true. No non-gun based spring company seems to make that claim.
 
See less See more
#2 · (Edited)
Good post and Wolff has come out with chrome silicon springs because of the demand made by those that claim them to be better. Wolff makes a disclaimer about the chrome silicon springs however, that they don't last as long as their HTCS proprietary spring wire. So take your pick something that lasts longer or something that is popular due to rumor.:biglaugh: Enjoy your toys.

LOG
 
#3 ·
Statement: http://www.ismi-gunsprings.com/

"Because of the properties of music wire; it cannot be heat treated, shot peened and stress relieved after the spring is wound."

Reality:

Music wire gets it strength from being cold worked and does not require heat-treat after forming. It must be stress relieved. One does not shot-peen music wire because it already has a perfect surface finish from the cold-drawing process.

"Per dwg 5013200 Rock Island Arsenal, Dept of the Army, 1 May 1928:
d = .043, OD = .430, free length = 6.55, active coils = 29, total coils = 30
8.00# @length of 3.72"
3.55# @length of 1.81"
2.88 #/inch
solid length = 1.375
music wire, qq-W-470
Stress relieve 20 minutes @450F after forming"


http://home.earthlink.net/~bazillion/finish.html

"Spring wire that gets bent has to have the bending stress relieved. Here are the stress relief guidelines for all common spring wire materials. Music wire, 500 degrees F for one hour"
 
#4 ·
...The way one designs a spring to not take a set is to physically not allow it to deform in a way where the stress exceeds the proportional limit. This may mean designing a pistol magazine to only take 12 rounds rather than 13, or add more coils to the spring, or use thicker wire, or use flat wire, or increase the OD. A properly designed system will allow for a fully loaded magazine to sit for over 100 years, or for an action to remain locked open without the recoil spring taking a set. Are some platform magazines improperly designed? Most certainly, but no one has seems to identify which ones. ...
Great post. I'm certainly not qualified to postulate, but the above excerpt is what resonates most with me.
 
#5 ·
See also, as always Brownell's for some easy to understand talk.

Gun Shop Work - Differences In Spring Rate Set Between Different Types of Spring Materials at http://www.brownells.com/aspx/NS/GunTech/NewsletterArchive.aspx?p=0&t=1&i=603

The test was done to compare Chrome Silicon springs, Stainless Steel springs, and Music Wire springs. ....

.....Music Wire springs ....have an operating temperature of around 250 degrees, but can be affected by 175 degree temperatures. ....

....I was surprised that the springs set in such a small amount between the different spring materials. Understandably, the test performed is not at all conclusive to the results one would find through shooting over a longer period of time.....
 
#9 ·
saltydog452 has an excellent point. The current standards for springs seem to be performance-oriented, rather than test-standard. If the springs aren't Mil-Spec, what is "standard" is anybody's guess.

Spring design is an art as much as a science. The use of gentle radius bends seems to be of more value than material. The sharper the radius of each bend, the more stress risers, and the quicker failure.

Mil-Spec springs, real ones, not just labels, will last quite well. Nothing that moves can do so without SOME wear, and will eventually fail. The idea that this or that is the "best" will usually require an explanation of under what conditions, and following what manufacturing limits.

I like Wolff music-wire springs. Of course, I don't expect my magazine springs, or recoil springs, to cycle forever. They are replaced at regular intervals.
 
#10 ·
A lot of posters have referred to Wolff springs being made of music wire which is a generic term. Wolff will deny that they use music wire and only designate it as special alloy to them and called HTCS spring wire, asked what the HTCS stands for will only get "it's proprietary to us". They state that their springs made from HTCS will have a longer life than any chrome silicon spring.

LOG
 
#16 ·
I totally am in agreement with Lilysdad. I have tried them all, and the ISMI springs have proven to be the very best FOR ME...... head and shoulders above the rest. I cannot address the experiences of anyone else. I have used ISMI springs for many years and they (for me) are like the "Energizer Bunny". They just keep going.....and going......and going.

Best regards,
Jeffro
 
#17 ·
I can't speak to differences in materials or manufacturers, but i can say that the few times i've tried the Chrome Silicon springs, the spring was noticeably lighter in terms of its poundage than advertised vs. the regular wolff wire springs. Where I can run an 18.5# spring when shooting +P loads with regular springs and have no problems, I tried this with the CS springs and it was like going down to a 16# or lighter, even though they were rated at 18.5#. Only by going up to a 20# did the CS match the perceived performance of the traditional springs. YMMV, etc.
 
#18 ·
rsilvers is precisely correct on his post. The Chrome Silicon buzzword is not always the answer. Proper spring design along with a proper selection of material is what makes a spring "not set" or "fatigue" in service. As far as spring design of a compression spring, the 3 factors that dictate spring rate are; wire size, active coils, and coil diameter. Knowing your furthest deflection of the spring from free length or inversely maximum cycle load point, helps with the design. If that max load point’s stress is less than 45% of the min tensile strength of the wire, everything is good. However more often than not in firearms, the springmaker is asked to meet load points considered "overstressed" in a design. (Like 10 lbs of sh** in a 5 lb bag) Then, things like pre-setting, and shot peening can be done to reduce the stress rate, but more often than not the springs are still considered "overstressed". When the application demands certain spring forces in small spaces, the only option is to have an overstressed spring(s) in the firearm. It's a fine line, but the firearm manufacturer must be aware of the consequences of the spring, being overstressed and a shorter cycle life expectancy.

BTW- HTCS stands for High Tensile Chrome Silicon. Your SWAG(Scientific Wild Ass Guess) was close. If anybody tells you that their material is proprietary, it’s more than likely a marketing gimmick. Ask to see the material certification along with the tensile test results from the mill, and more than likely it’s produced to ASTM A 401.
 
#21 ·
Yes, but only an Officer model (3.5") with an Ed Brown single spring and guide rod. At somewhere around 500 rounds it would fail to return to battery. But that was eventually cured with the EGW flat wire spring.
 
#22 · (Edited)
Dare say HTCS means High Tensile Carbon Steel since they say it lasts longer than Chrome Silicon.

A characteristic I hope you don't run into, a lot of my gear was subjected to steam, water, smoke and fumes in a house fire. (But flame did not get to my magazines.)
The chrome silicon springs were all badly corroded and I am replacing them as I discover them and place orders. Some of the carbon steel springs were corroded, but not all, and those not as badly.


Ever notice that the stories you read about guns found loaded for 50 years shooting reliably are generally GI guns with 7 round GI magazines? Also that recent makes of 8 round magazines steal enough protrusion for an extra coil of spring by disguising it with a wrap-around basepad. In the early days of flush 8 round magazines, I had to replace the springs periodically. Fortunately, they showed wear by failing to slide stop before they got bad enough to quit feeding.
I think that shows the importance of proper design of springs meant to be deflected a long way. Recoil and magazine springs are not like car valve springs that only flex a fraction of an inch. But the mainspring IS and it is typically a lifetime part.
 
#25 ·
I use Wolff Recoil springs, 18lb(Except for my Gold Cup which I run a 16lb. Wolff in). I usually change them out every time the shotbook shows 3000 rounds. According to my notes, Free-Length on the Wolff spring is the same at 3000 as it is at 500 rounds. I'll also add that, when I change the spring out there's no difference in performance which leads me to think that the life of the spring could actually be longer. I use one load for 98% of my shooting with my 1911s, 5.2 grains of HP-38 and a 230, either a FMJ or a RNL. This is a chrono'd 835fps load.

I did try a Chrome-Silicon 18lb.spring once. At 2000 rounds I could tap the slide at the muzzle with my finger and the slide would move backwards about 1/4"(Hammer cocked, gun empty). Never been able to do that with a Wolff spring. For the record I can't remember who manufactured the Chrome-Silicon recoil spring, only that I got another Wolff out of the bin and promptly replaced it.
 
#26 ·
I thought HTCS meant "Highly Technical Custom Stuff."
 
#33 ·
More or less what he suggests, but the HTCS is common in the spring wire supply industry to mean High Tensile Carbon Steel as evidenced by the link provided. Wolff does make and sell chrome silicon 1911 springs, but states they do not have as long a life as their std. spring material. Wolff is hard to beat.

LOG
 
#34 ·
Luv ya, log man, but your link doesn't use the acronym HTCS.

The link is a chinese company, and it does discuss its high tensile carbon steel, which content shows that it does not meet ASTM A-401 for chrome silicon wire, so it is carbon steel. No question about that. But I didn't find the acronym HTCS.

I looked up HTCS in our engineering reference guides and it is not an industry defined acronym.

So when it comes down to it, the nomenclature really doesn't matter. Certain manufacturers have superior products, and each of us learns that through experience.





For the record, the OP uses the term 'not taking a set'. Actually, we have found that fatigue is the enemy of springs, not the free length set it takes after initial loading. But the OP's discussion seems to talk about fatigue, so I think that's the real subject of the thread.
 
#36 ·
Yes, my friend, no argument from me. I'm just thinking that Wolff and IMSI and all those folks are holding more behind the screen that they aren't showing us and never will. We'll never really know what material they use.

So bottom line is performance. We know what performs.



By the way, any idea why other types of guns cycle their springs as much as a 1911 (like autoloading shotguns) but the spring lasts a lifetime? We're still using the same action spring and recoil spring in grandpa's Rem Mod 11 shotgun from 1932, probably 100,000 cycles by now, the action spring is about the same diameter & wire as a 1911 recoil spring and gets compressed the same. Like the Energizer Bunny it just keeps going...
 
#37 ·
I have been using ISMI springs for 6 years or so. They certainly take less of a "set", and lose less of their uncompressed length after use over the long term than Wolff springs. This obviously subjective opinion is based on year of shooting each spring in a 5" 1911 Colt, built by Novak's, using only hardball (I quit reloading years ago).

Either make spring is cheap, in the big picture. If I ever have any doubt as to the age or condition of any particular spring, I pitch it and install a fresh one. Cheap insurance.

Marc Cosat at ISMI certainly does not seem to be hiding any information. He is a delight to talk to about the technical aspects of his springs.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top