Chrome Silicon Wire..... the future of gunsprings!?

[tex_n_cal]

Let me comment that I work for _____Spring Co, have been there for nine years, and prior to that worked for ____ Spring Division of _____Corp for nine years. I don't sell gun springs, so you can assume that I don't have any axes to grind.

Chrome silicon in one variety or another is used in suspension springs, as well as engine valve springs. In both cases, we're using more and more 9258+V materials, which can be very hard, yet still tough.

Chrome silicon in one variety or another does have somewhat better long-term sag resistance than carbon steels, like music wire. 1000x better? No way.

My personal opinion is that so-called "rocket wire", or high-tensile music wire is really a better choice for gun springs, if it is processed correctly. There are lots of subtle tricks in making springs, and material choice is only one of them. In the small wire sizes used in recoil springs, rocket wire has higher tensile strength than chrome sil, based on a perusal of current SAE and ASTM specs for the wire. 17-7 is an excellent spring wire, too, if stainless is desired.

Titanium springs? BTDT. In a mainspring, they will theoretically release their energy faster, by a smidgeon, due to its higher energy storage per mass. Make a practical difference in a gun? Maybe if you're trying to get 5000 rpm, otherwise no. They really work better on larger springs, where weight, space, or corrosion is an issue.

One of these days I really need to start my own gunspring business

 

[Sven]

Let me know if you need investors.

 

[COOL]

USPSA and IDPA shooters have used http://www.ismi-gunsprings.com/navigation.html
for years.

 

[rsilvers]

BTW, it is marketing BS that CS springs are superior to stainless. Especially 17-7 stainless is great.

The advantage of CS over music wire is that they are 475 degree rated rather than 250. However, stainless is even higher temp and in some alloys with no loss of spring properties compared to CS.

 

[DBR]

It is also a magazine design issue. Many modern high cap magazines (esp pistol) exceed the normal engineering parameters for acceptable spring stress given the quality of the issued springs.

After market, better quality springs can sometimes help rectify this problem.

Conservative magazine design (under loading) is better.

 

[DBR]

Music wire springs, even good quality ones, are at the bottom of the food chain endurance wise. Why would anyone in the gun spring business make the "ultimate spring" that never has to be replaced? To stay in business they would have to charge so much no one would by their springs.

Some gun designs assume short spring life in their specs. The problem I have with this is if the weapon is intended for self defense the owner never knows where they are in the spring life/reliability cycle.

OEM manufacturers (usually) only want the least expensive option that will make their product reliable for the average user (who may hardly ever shoot the gun).

For things like 1911 recoil springs, AR15 ejector and extractor springs and "under designed" mag springs in Glocks, Berettas and many other hicaps, after market CS springs can be real benefit IMHO.

The alternative to high quality springs is very conservative design. For example AK47, SKS and other low end military designs. The price is lower capacity and usually heavier weapons.

 

[kilo729]

If I'm not mistaken these things rust faster than SS.

 

[Tinman357]

I have IMSI springs in the two guns I carry to defend my daughter and myself. Nuff said..

 

[DBR]

In my experience CS is no more prone to rust than music wire. CS does sometimes have a coating of oxide from heat treating that looks like rust. If they are properly shot peened after heat treating they are dull black.

I wipe down all off my gun springs with a patch using Eezox. CLP works about as well. I have never had a mag spring (or any other spring) fail from rust. Have you?

For the anticipated non military uses I think there are benefits to CS springs. 17-7 alloy springs are also excellent but they are not generally available except for AR mags.

 

[rsilvers]

It does seem possible that some gun mag springs are designed outside the limit of spring technology. If I ever learn of such a gun I will never buy it.

I am going to analyze the 1911 spring and post a report.

 

[rsilvers]

Interesting. My initial analysis is that a 1911 spring in full recoil is over-stressed. I am getting 60% of tensile. A spring should not go over 45%. A 1911 spring at full recoil is 1.62 inches long and really it would be good to never let it go below 2.8 inches long.

 

[Justin]

This thread was started a few years ago. Usually the policy is to close threads that are pulled up from so long ago. However, in this case, the content is good enough that I'm not going to close this one.

 

[rsilvers]

Wolff Springs now has CS.

"While Chrome silicone is and excellent material, it is a softer material and does not offer the tensile strength of our proprietary HTCS spring material - the material most of our springs are produced from. We now offer these springs due to customer requests. "

I see they got tired of telling people CS was not the best material and figured it was easier to just sell it.

 

[DBR]

It isn't the tensile strength which is of concern in spring design. It is the "proportional limit" which is less than the yield strength of the material.
http://www.ae.msstate.edu/~masoud/Teaching/SA2/def.proportional_limit.html

There is another issue with recoil springs. Even if the spring is OK at full design static compression, unless it is not over stressed at "coil bind" the compression wave that runs down the spring during dynamic recoil may over stress it.

Because of the very low cycles a mag spring sees it can be designed closer to the proportional limit than normal spring design criteria. Never the less many mag springs are still overstressed.

 

[DBR]

Not to nit pic: but the material is "chrome silicon". "Silicone" is usually an elastomer.

 

[rsilvers]

Yes but that is the same as what I said because the amount of stress where the strain gets out of proportion occurs at 45% of the minimum tensile strength of chrome silicon, 17-7, and music wire. So in effect, all that matters is minimum tensile strength of each of those materials.

For music wire, it is 230-399 KSI. For chrome silicon, it is 235-300 KSI. For 17-7, it is 235-335 KSI.

From this data, one can see that there are types of music wire which have higher tensile strength properties than the best chrome silicon. And since the 45% ratio applies for both, then music wire can be LESS likely to take a set than CS.

For a recoil spring, is a marketing trick that seems to have worked. For higher temp apps, that is another matter.

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

 

[rsilvers]

That was just a quote from Wolff's web page.

 

[rsilvers]

I would love if someone would compile a list of semi auto pistols who's factory magazines, when fully loaded, had a ratio of stress to min tensile strength of more than 45%. We might learn that such-and-such's 12-round .45 is really an 11 round .45. This would be one more tool to help decide on a platform.

 

[DBR]

There is another interesting thing I've noticed re music wire. If I try to bend an ISMI CS spring is takes quite a bit of force but when it does bend (take a set) it does it "all of a sudden" like the wire got soft. If I do the same thing with a Wolff music wire spring it resists all the way.

It seems the ISMI CS spring material has quite a dip after the yield point is reached. Does it matter? I don't know. The only feeling it leaves me with is a CS spring might be more likely to break compared to a music wire spring which just seems to weaken.

There are other relevant material issues such as fatigue resistance and "toughness". I don't know where the two materials score here.

 

[DBR]

There is another difference between music wire and other springs. As far as I know music wire is wound cold with no further processing. Most CS springs are wound then heat treated and stress relieved. To fully understand the stress situation with a music wire spring it seems some allowance needs to be made for the residual stresses in the wire after winding.

Maybe I'm over thinking this but there has to be some reason why a Wolff 1911 recoil spring is getting tired after 3000 rounds and an ISMI spring shows no change.

I think it probably relates to the fatigue resistance of the material.

 

[rsilvers]

Cold wound springs always need to be stress relieved -- that is how they become at rest with their new shape. It is hot-wound which do not.

I believe there is a big fatigue issue with 1911 recoil springs. Every time I plugged the USGI 1911 spring into a spring calculator, it warned me about fatigue for that design.

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

Does the Woff and ISMI have the same number of coils and the same wire diameter?

 

[rsilvers]

http://www.brownells.com/aspx/NS/GunTech/NewsletterArchive.aspx?p=0&t=1&i=603

"Chrome Silicon springs can withstand temperatures of 1300 degrees maximum. This is far more than what is required in most firearms."

This is not true. They are only rated to 475 degrees. If you want to go higher, there is stainless steel.

http://www.mwspring.com/materials.html

I suspect the set can be explained more by the heat-treat or stress relieving of the material than by the alloy itself.

Also I did not see the wire diameter in the test. Was it the same for each alloy?

 

[rsilvers]

http://books.google.com/books?id=08...X&oi=book_result&ct=result&resnum=9#PPA300,M1

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."

Since a 1911 spring is 0.043 wire, and since it is an application below 250 degrees F, music wire is best. Chrome Silicon is speced for engines only due to the high temp environment.

 

[rsilvers]

Both hard drawn wire and music wire gain their
strength through cold drawing the wire from large
diameter rod to its final size. There are three
significant differences. First is the chemical
composition of the wire. Music wire contains more
carbon and less manganese than hard drawn wire.
Additionally, the allowed levels of contaminants such
as phosphorus and sulfur in music wire are more
restrictive. The second key difference is in the wire’s
strength. Because of the additional carbon, music
wire can be drawn to significantly higher tensile
strengths than hard drawn wire. Finally, 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. Hard
drawn wire is best suited to static or very low cycle
service conditions.

 

[DBR]

What Wolff has sold as a "standard" 1911 recoil spring is .0445 wire with 32 coils. The end coil on one end is closed so call it 31 coils. On my spring tester it shows 8-8.5# at in battery length and 17# +- at full recoil length. This is a spring with about 500 rds on it.

The 18# Wolff springs I have are 31 1/2 coils for .045 wire. Again with a closed coil on one end. They test 9# in battery and 18#+- at full recoil

ISMI seems to use .044 wire and 32 coils for the "16#" spring and 30 coils for the "18#" spring. The free length of the ISMI spring is longer and it stays longer than the Wolff by about 1/2" after several hundred rounds. The ISMI springs are about 9# in battery and between 16 and 17# at full recoil. They also have a closed coil on one end.

This info is from memory. I think it is accurate. All of these springs were purchased at least five years ago.