SD aftermarket guide rod/spring analysis thread

[huafist]

So, based on the discussion we were having in this thread:
SD40VE ~1600 rds, broken frame/slide takedown lever issue

I decided to start a new topic, as suggested by 3hounds. Based on our discussions, I actually ordered an SS guide rod from stainless steel guide rods, Inc on Amazon yesterday. I'm going to do some testing with the 20lb spring that comes with it, as well as the stock spring. I'll be checking:

1) Free length of each spring, as well as distance between coils uncompressed.
2) Distance between coils at install height.
3) Coil bind (stacking) on both springs.
4) If I have the time, I'll check preload and max compression load numbers.

[Steve912]

Include the thickness of the rod base also, in overall length of compressed spring stack.

[40s&w]

Who makes the springs for stainless steel guide rods Inc?

[3hounds]

Which guide rod did you order ?

Oh I see they actually make one for our guns, nice.

ISMI believed the Gock 19 guide rod and spring should work
in our guns.

Mine didn't as you know, spring is too long.

Thanks, 3

[Disabled1]

After a few months with the Galloway SS Glock 19 guide rod assembly in my SD9VE, I have shot WELL OVER 1K rounds of anything from 115 gr to 147 gr in it, and had NO FTE, FTF, or FTF's! I would have to say that installing the $12 cheaper in price Glock SS guide rod over the recommended $12 more required S&W SDVE SS guide rod assembly, was a great choice!

[ou1954]

Originally Posted by huafist

So, based on the discussion we were having in this thread:
SD40VE ~1600 rds, broken frame/slide takedown lever issue

I decided to start a new topic, as suggested by 3hounds. Based on our discussions, I actually ordered an SS guide rod from stainless steel guide rods, Inc on Amazon yesterday. I'm going to do some testing with the 20lb spring that comes with it, as well as the stock spring. I'll be checking:

1) Free length of each spring, as well as distance between coils uncompressed.
2) Distance between coils at install height.
3) Coil bind (stacking) on both springs.
4) If I have the time, I'll check preload and max compression load numbers.

It would be beneficial to also measure the spring rate if you do have a decent scale and distance measuring tool. You might be able to derive it from the measurements you intend to make.

[Sidnne]

Originally Posted by Disabled1

After a few months with the Galloway SS Glock 19 guide rod assembly in my SD9VE, I have shot WELL OVER 1K rounds of anything from 115 gr to 147 gr in it, and had NO FTE, FTF, or FTF's! I would have to say that installing the $12 cheaper in price Glock SS guide rod over the recommended $12 more required S&W SDVE SS guide rod assembly, was a great choice!

I shot about 1,500 rounds with the Galloway spring before my frame broke.

[huafist]

Originally Posted by Steve912

Include the thickness of the rod base also, in overall length of compressed spring stack.

Of course As well as the thickness of any washers at the other end of the rod.

[huafist]

Originally Posted by ou1954

It would be beneficial to also measure the spring rate if you do have a decent scale and distance measuring tool. You might be able to derive it from the measurements you intend to make.

I figured could get it using the spring rate formula
(k = (d^4G)/(8D^3N))

However, after a little time, it occurs to me that the guide rod springs are flat wire, not round. I don't think I can derive an accurate value for (d) in the above equation with flat wire?

***EDIT 2***
I'm an idiot. I can treat it like a rectangle and find it's diagonal length.

[4MUL8R]

There is a different formula for flat wire springs. If I hadn't turned in my mechanical engineering handbooks I would give it to you. You can measure load at two compressed lengths and obtain the rate directly. Keep in mind that as coils begin to touch that the rate can change.

[huafist]

Originally Posted by 4MUL8R

There is a different formula for flat wire springs. If I hadn't turned in my mechanical engineering handbooks I would give it to you. You can measure load at two compressed lengths and obtain the rate directly. Keep in mind that as coils begin to touch that the rate can change.

Good to know. I'll see if the all-knowing google will turn up the rate formula for the flat wire coil spring.

[ou1954]

Originally Posted by huafist

Good to know. I'll see if the all-knowing google will turn up the rate formula for the flat wire coil spring.

No objection to scientific research [my old home] but I would be much more comfortable with direct measurements of real springs. I understand that someone in this thread is going to do that this weekend.

We know nothing about the characteristics of the spring material, so even with a perfect formula there are still many unknown variables.

ISMI says: "All Springs are Heat Treated, Shot Peened & Stress Relieved" so I'm not sure where that leaves us with regard to the material properties.

ISMI also seems to admit that spring characteristics do change with use, although probably not much in a gun, but of course, a lot in a race car.

[huafist]

Originally Posted by ou1954

No objection to scientific research [my old home] but I would be much more comfortable with direct measurements of real springs. I understand that someone in this thread is going to do that this weekend.

We know nothing about the characteristics of the spring material, so even with a perfect formula there are still many unknown variables.

ISMI says: "All Springs are Heat Treated, Shot Peened & Stress Relieved" so I'm not sure where that leaves us with regard to the material properties.

ISMI also seems to admit that spring characteristics do change with use, although probably not much in a gun, but of course, a lot in a race car.

I agree 100% ; I'm just curious as to how close the numbers in the real world are to what the math says they should be. However, instead of digging around looking for something that I may or may not find based on terminology used, I think we can agree that the best real world method is k=F/x.

I've already taken apart a stock guide rod and done some force measurements on it, and I'll do the aftermarket after it gets here tomorrow. Hopefully we'll find some useful data this way.

[TriumphMan]

? for the guru's.

A slide spring has 4 things going on.

1: preload

2: spring poundage/rate

3: over-all compression length

4: rebound

What point of a spring is measured to consider it's weight rating for a gun's slide?

What I mean, is the spring divided into sections for measurements? Like the first 1/5rd is your preload, then 1/5 to 3/4 of spring length is where poundage is measured and last 1/3 of spring the weight doubles, while not stacking, to build up compressed energy for the ejection and next round/feed rebound, while all the time also pushing the weight of slide back/forwards.

[huafist]

So, the SS guide rod came today:

Amazon.com : Smith and Wesson SD9VE/SD40VE Stainless Steel Guide Rod Assembly (Drop-in Ready!) : Sports & Outdoors

 

Amazon.com : Smith and Wesson SD9VE/SD40VE Stainless Steel Guide Rod Assembly (Drop-in Ready!) : Sports & Outdoors

In overall lenth, it's only .003" longer than the stock polymer rod - and that's at the captive screw, which sticks out of the slide anyway. Other than that, the dimensions are identical.
I installed the spring and checked slide travel - the slide stops in the EXACT same spot as it does with the stock rod. Travel is identical.
The spring is definitely stiffer than stock, but my scale gave up the ghost on me when I tried to measure it (it won't do anything now but put '8888' across the LCD).

At installed height, the air gap between coils was only .0005" difference from the stock spring, on the wider side.

I'm going to pick up another scale this week and hopefully get some better information for everyone over the weekend.

[huafist]

Originally Posted by TriumphMan

? for the guru's.

A slide spring has 4 things going on.

1: preload

2: spring poundage/rate

3: over-all compression length

4: rebound

What point of a spring is measured to consider it's weight rating for a gun's slide?

What I mean, is the spring divided into sections for measurements? Like the first 1/5rd is your preload, then 1/5 to 3/4 of spring length is where poundage is measured and last 1/3 of spring the weight doubles, while not stacking, to build up compressed energy for the ejection and next round/feed rebound, while all the time also pushing the weight of slide back/forwards.

While I'm not a "guru", the numbers crunching that I've done so far leads me to believe that's a full travel of the slide. I'll post numbers later to show my work.

[ou1954]

Originally Posted by TriumphMan

? for the guru's.

A slide spring has 4 things going on.

1: preload

2: spring poundage/rate

3: over-all compression length

4: rebound

What point of a spring is measured to consider it's weight rating for a gun's slide?

What I mean, is the spring divided into sections for measurements? Like the first 1/5rd is your preload, then 1/5 to 3/4 of spring length is where poundage is measured and last 1/3 of spring the weight doubles, while not stacking, to build up compressed energy for the ejection and next round/feed rebound, while all the time also pushing the weight of slide back/forwards.

Spring rate is simply the force required to compress the spring a specific distance and is, in our application, pounds per inch of compression. It is (almost) independent of how much it is compressed. Also, it applies to the spring as a whole, but one can also take measurements of intermediate sections of the spring and get the same result.

If the free length of a spring is 2 inches and a force of 20 pounds compresses it to a length of 1 inch the spring rate is 20 pounds per inch. If the spring "stacks" when being tested the result is meaningless.

I sometimes wonder whether the theory of "suddenly applied loads" comes into play in gun spring design. Look it up, it's an unexpected effect and something everyone remembers from most mechanical or stress classes. (We remember the result/effect but usually can no longer state the formula. I had to look it up.)

[huafist]

Originally Posted by ou1954

Spring rate is simply the force required to compress the spring a specific distance and is, in our application, pounds per inch of compression. It is (almost) independent of how much it is compressed. Also, it applies to the spring as a whole, but one can also take measurements of intermediate sections of the spring and get the same result.

If the free length of a spring is 2 inches and a force of 20 pounds compresses it to a length of 1 inch the spring rate is 20 pounds per inch. If the spring "stacks" when being tested the result is meaningless.

I sometimes wonder whether the theory of "suddenly applied loads" comes into play in gun spring design. Look it up, it's an unexpected effect and something everyone remembers from most mechanical or stress classes. (We remember the result/effect but usually can no longer state the formula. I had to look it up.)

Since I'm not a mechanical engineer, just a nerd - would that "theory of suddenly applied loads" work in the same manner as a non-Newtonian fluid? ie, the more suddenly force is applied, the stiffer the response?

[huafist]

Ok, so here are some numbers on the stock spring. I'll have to get another scale before I can go any further, as mine died during testing.

Overall free spring length: 4.996"
Spring installed height: 2.995"
Given that the slide travels rearward 1.885" at full recoil, that means the spring has a maximum compression of 3.886" during operation.

I took compression force measurements every 0.5" for the first 2" of spring travel - I couldn't go any further due to my scale issue. However, that's been enough to get some good data:

4.996": 0.0lbs
4.496": 2.1lbs
3.996": 4.1lbs
3.496": 6.3lbs
2.996": 8.6lbs

So this means that the preload on the spring is ~8.6lbs. We've worked it out to a spring rate of 4.1lbs, which gives us 15.93lbs at full recoil.

[ou1954]

Originally Posted by huafist

Ok, so here are some numbers on the stock spring. I'll have to get another scale before I can go any further, as mine died during testing.

Overall free spring length: 4.996"
Spring installed height: 2.995"
Given that the slide travels rearward 1.885" at full recoil, that means the spring has a maximum compression of 3.886" during operation.

I took compression force measurements every 0.5" for the first 2" of spring travel - I couldn't go any further due to my scale issue. However, that's been enough to get some good data:

4.996": 0.0lbs
4.496": 2.1lbs
3.996": 4.1lbs
3.496": 6.3lbs
2.996": 8.6lbs

So this means that the preload on the spring is ~8.6lbs. We've worked it out to a spring rate of 4.1lbs, which gives us 15.93lbs at full recoil.

Very valuable measurements . . .

So, we've been discussing spring rate here and assumed it was in the range of 16-22 pounds per inch.

It now seems clear that when a vendor talks about a 16 or 22 pound spring it's clearly not the technical spring rate.

Any thoughts?

[3hounds]

I emailed Stainless Steal Guide Rods Inc.

I asked who makes the springs for their SD40VE rods.

Response was, they use the factory S&W spring.

When a vendor talks about a 16 or 22 pound springs, their talking about
that poundage at full slide for said gun.

3

[huafist]

Originally Posted by 3hounds

I emailed Stainless Steal Guide Rods Inc.

I asked who makes the springs for their SD40VE rods.

Response was, they use the factory S&W spring.

When a vendor talks about a 16 or 22 pound springs, their talking about
that poundage at full slide for said gun.

3

No kidding?
Well that brings me to one of two conclusions then:
1) The spring is stiffer than the one I removed because it's new.
or
2) The hand equivalent of the "butt dyno" lied to me and there's no difference at all.

But, what you say would explain the measurements I took of the springs...

***EDIT*** I wonder if they're using the factory spring for the 9mm as well? That's what I'm testing.

[3hounds]

I actually had t o contact them twice.

Original question I asked was, Who makes the springs for
your Guide Rod's.

Reply was, We use different makes of springs depending on
the model you are interested in.

They wanted to know which model, so they could tell me which
spring they were using. I told them S&W SD40VE.

Now from what I've been told the 9 and 40 factory springs are
the same, according to S&W ?

I don't think they should be that's why I went with the aftermarket NDZ
rod and spring rated at 20 lbs.

That led to the dilemma we are discussing now.

I wonder how their getting their hands on factory springs ?

You are correct, a new spring will have to be compressed to take
a set, so they will feel stronger before that time.

3

[huafist]

Originally Posted by 3hounds

I actually had t o contact them twice.

Original question I asked was, Who makes the springs for
your Guide Rod's.

Reply was, We use different makes of springs depending on
the model you are interested in.

They wanted to know which model, so they could tell me which
spring they were using. I told them S&W SD40VE.

Now from what I've been told the 9 and 40 factory springs are
the same, according to S&W ?

I don't think they should be that's why I went with the aftermarket NDZ
rod and spring rated at 20 lbs.

That led to the dilemma we are discussing now.

I wonder how their getting their hands on factory springs ?

You are correct, a new spring will have to be compressed to take
a set, so they will feel stronger before that time.

3

Now that doesn't make sense - I don't see why a 9 and a 40 would have the same recoil spring ; the mass of the projectile is different.

[ou1954]

After all my (and other folks) learned discussion about spring rate, the technical definition of it, etc., it seems that the numbers given by vendors for "spring weight" are not the spring rate but apparently the ultimate force exerted by a spring at full recoil. So much for "exact science".

I sent the measurements posted by huafist to my contact at ISMI and am waiting for a response.

[ou1954]

I sent a second email to ISMI as follows:

To: (Marc Cosat) <[email protected]>
Subject: Spring rate


One of the S&W forum members ran some tests on a free spring from his SD gun. I asked him to measure the force vs spring length and he did a great job, as follows:

Results of his test

Length Force applied
4.996" 0.0lbs
4.496" 2.1lbs
3.996" 4.1lbs
3.496" 6.3lbs
2.996" 8.6lbs

His data seems to say that the scientific "Spring Rate" is about 4.1 pounds per inch.

His scale failed before he could go to a greater force but when he extrapolated to the full-recoil length he got a force in the 16# range.

The question is, when a vendor says the "Spring weight" is 16 pounds, does he mean that the force is 16 pounds at the full recoil length?

Please let me know so I can post the correct specification definition on the forum.

[ou1954]

For those who have contacted vendors other than ISMI, the one I have contacted, I think it would make sense to send them a version of the email to ISMI I just posted.

Previous emails to them resulted in a rapid response. So far nothing on the new measurements.

[huafist]

So, I meant to go to the range this afternoon and put about 50 rounds through the gun, but the wife texted me about the time I got off work and wanted to meet for dinner, since our son is gone away to military summer camp. I'll get by there tomorrow and come back with results. I installed a set of TruGlo fiberoptic sights also, so I'm anxious to see what it'll do.

[ou1954]

Originally Posted by huafist

So, I meant to go to the range this afternoon and put about 50 rounds through the gun, but the wife texted me about the time I got off work and wanted to meet for dinner, since our son is gone away to military summer camp. I'll get by there tomorrow and come back with results. I installed a set of TruGlo fiberoptic sights also, so I'm anxious to see what it'll do.

I finally got a response from ISMI and responded to it. I sent a PM to you with their response to my report of your test results and my response back to them. I was not impressed by their response so I won't post it on this thread.

[huafist]

Originally Posted by ou1954

I finally got a response from ISMI and responded to it. I sent a PM to you with their response to my report of your test results and my response back to them. I was not impressed by their response so I won't post it on this thread.

Agreed. It was not professional in the least, and still didn't answer anything.

[3hounds]

I'm getting confused on which spring he tested, who makes springs for who ?

Thought it was stock spring he posted results from ?

Does ISMI make the stock springs for S&W ?

Looked at the new guide rod and spring you bought on
Amazon, it doesn't specify what pound the spring is that
I could find ?

3

[ou1954]

Originally Posted by huafist

Since I'm not a mechanical engineer, just a nerd - would that "theory of suddenly applied loads" work in the same manner as a non-Newtonian fluid? ie, the more suddenly force is applied, the stiffer the response?

It's an old surprise in strength of materials courses. Something you remember forever, (well, for at least 66 years in my case) but never use in the real world.

Here is a basic discussion.

Assume you have a beam freely supported near the ends (say sitting on sharp rails). You gently place a weight on the center of the beam and it deflects 1" after all movement stops. You drop the weight from some height and it's clear that it deflects more than 1" until it settles. So far, so good.

Being a good student you derive an equation to find maximum transient deflection vs height of drop. Then you run the drop height to zero. Surprise, the deflection is 2".

If you could just hold the weight on the beam and release it suddenly, the deflection would be our derived 2".

In the real world such things as friction, resonant frequency, etc., affect the result.

This effect is important in bridge design because a vehicle suddenly appears (as far as the slow old bridge is concerned). Well, the reality is that there are many other real world factors so that the suddenly applied load doesn't much matter.

Now, having said all that, I can't say whether the impulse of firing a gun counts as a suddenly applied load. Just an interesting thought.

[huafist]

Originally Posted by 3hounds

I'm getting confused on which spring he tested, who makes springs for who ?

Thought it was stock spring he posted results from ?

Does ISMI make the stock springs for S&W ?

Looked at the new guide rod and spring you bought on
Amazon, it doesn't specify what pound the spring is that
I could find ?

3

It was a stock spring that I tested.

I assumed at purchase time it was 20#, but I don't know that for sure. I did run about 50 rounds of 115gr FMJ through the gun last night, and had 2 failed ejections - the slide returned to battery too quickly and caught the casing mid-flight. I'm hesitant to say this is a problem until I've ran a few hundred rounds through the gun to "break in" the spring.
Gun definitely feels more "mechanical" than before, if that makes sense.

[huafist]

Originally Posted by ou1954

It's an old surprise in strength of materials courses. Something you remember forever, (well, for at least 66 years in my case) but never use in the real world.

Here is a basic discussion.

Assume you have a beam freely supported near the ends (say sitting on sharp rails). You gently place a weight on the center of the beam and it deflects 1" after all movement stops. You drop the weight from some height and it's clear that it deflects more than 1" until it settles. So far, so good.

Being a good student you derive an equation to find maximum transient deflection vs height of drop. Then you run the drop height to zero. Surprise, the deflection is 2".

If you could just hold the weight on the beam and release it suddenly, the deflection would be our derived 2".

In the real world such things as friction, resonant frequency, etc., affect the result.

This effect is important in bridge design because a vehicle suddenly appears (as far as the slow old bridge is concerned). Well, the reality is that there are many other real world factors so that the suddenly applied load doesn't much matter.

Now, having said all that, I can't say whether the impulse of firing a gun counts as a suddenly applied load. Just an interesting thought.

I see what you're saying. It's definitely something to think about.

[TriumphMan]

Received new Spring from Galloway Precision Today.

Here are measurements, test results before and after modifications that WERE REQUIRED.

Spring OAL out of package: 5.190"

Coil Thickness: .027"

Coils: 28

Air Space between Coils: .060"

Spring (outside) Diameter: .415"
This was something I measured between this spring and 16# spring and there was a difference of: .002
16# spring was .417(larger and lower poundage) uuuuummm.

DO NOT USE this spring with out cutting off coils. It's too long and is wavy on Rod when installed. Slide doesn't like this spring when it's too long.
It did work in gun, but I had to use moderate hand blows on slide to get off after firing 1 magazine, then doing a takedown to check parts.
It did cause some light Rod hammering on the Take-down Plate Ears.

Cut Spring now works great in SD9VE.

Spring Length (CUT): 4.185"
Total around 4 coils cut.
Coils after cut: 24
Difference in length between (new) and (cut) spring: 1.005"


You guys, like me, could you check the outside diameter of your stock and aftermarket springs? This might be where some rating/poundage is coming from.

I have a 16# and now 19# springs, but the diameters were different and I want to see if you guys get same result in finding the higher poundage spring to be smaller in(outside) diameter to gain compression forces in higher rating, while also being thicker in coil thickness and if this really might make some difference to how some springs get their ratings, while still looking like it's identical lesser poundage spring.

I'm thinking if a spring's outside diameter is smaller, that forces needed to compress go up, as long as coils are also thicker and act as fulcrum between each coil to raise the poundage rating over the length of spring.

Like someone mentioned with a car's leaf spring package. The shorter(in our instance), the TIGHTER the coil wind, with thicker coils, the more force needed to compress.

I ask this because the new 19# spring is now shorter than the 16# spring, but is smoother to shoot due to higher rating and the heavier coils.

Does this sound plausible?

Also, not having a spring scale, my hands are telling me the gun is smoother in action.

I hope I got all my measurements in, that you can understand. I have a lengthy writeup in the other section about 1600 rds and broken frame, but some of the stuff I wrote here is more from my thought about the spring's diameter that I had go through my head about spring ratings.

[ou1954]

I would not suggest using a spring the vendor suggested modifying in any way.

It's just not a professional approach.

[ou1954]

"Spring weight"

I just found this little tidbit on the Wolff spring web site-

"LOAD-RATED RECOIL SPRINGS are precision springs designed to exact load ratings. The load rating of these springs is determined with the slide in full recoil position"

[ou1954]

Wolff FAQ uses the term "pound of energy" in their FAQ section.

Energy could be expressed as "inch-pounds" but not just "pounds". That bothers me.

[3hounds]

Originally Posted by ou1954

I would not suggest using a spring the vendor suggested modifying in any way.

It's just not a professional approach.

Believe me it's very normal, not just by the vendor but the manufacturer.

3

[ou1954]

Originally Posted by 3hounds

Believe me it's very normal, not just by the vendor but the manufacturer.

3

I really didn't know it was common practice. I would guess, however, that S&W would not approve. I've never wanted to change my spring weight so I never encountered the issue.

Actually it was only today that I finally got a clear definition of what the manufacturers call "Spring Weight", something we slowly realized in these two threads. I had asked several vendors but never got an response that made sense.

Today I found the definition, at least for the Wolff spring company, buried in a single sentence in their FAQ section.

Now anyone with an inexpensive spring scale can measure "Spring Weight", quite easily.

[huafist]

Originally Posted by ou1954

I really didn't know it was common practice. I would guess, however, that S&W would not approve. I've never wanted to change my spring weight so I never encountered the issue.

Actually it was only today that I finally got a clear definition of what the manufacturers call "Spring Weight", something we slowly realized in these two threads. I had asked several vendors but never got an response that made sense.

Today I found the definition, at least for the Wolff spring company, buried in a single sentence in their FAQ section.

Now anyone with an inexpensive spring scale can measure "Spring Weight", quite easily.

You know, before I saw this, I was only slightly insulted by the reply you got from ISMI. Now, I'm VERY insulted by it.

[ou1954]

Originally Posted by huafist

You know, before I saw this, I was only slightly insulted by the reply you got from ISMI. Now, I'm VERY insulted by it.

(For folks who may be following this general subject, huafist has received "off list" copies of correspondence between me and some spring companies. I did post one message from ISMI but asked for permission first. I won't post the others unless I request, and receive, permission to do so.)

It will be interesting to see whether Wolff responds to my question about energy being expressed in "pounds".

I am also surprised to see Wolff say that piano wire is the only way to go and ISMI say that piano wire has un-controlled characteristics and flat springs are best for recoil applications.

I have only a little experience with a variety of guns but I am pretty sure Glock and S&W use only flat "wire" in their recoil springs.

[huafist]

Originally Posted by ou1954

(For folks who may be following this general subject, huafist has received "off list" copies of correspondence between me and some spring companies. I did post one message from ISMI but asked for permission first. I won't post the others unless I request, and receive, permission to do so.)

It will be interesting to see whether Wolff responds to my question about energy being expressed in "pounds".

I am also surprised to see Wolff say that piano wire is the only way to go and ISMI say that piano wire has un-controlled characteristics and flat springs are best for recoil applications.

I have only a little experience with a variety of guns but I am pretty sure Glock and S&W use only flat "wire" in their recoil springs.

So, I just checked the RSAs in several of my guns:
Springfield XDm .45
Springfield XDm 9mm
Taurus PT24/7 Pro .40
SCCY CPX2 9mm
S&W Bodyguard .380

ALL of them have round wire springs.
The Taurus, SCCY, and, curiously, the Bodyguard all have dual spring assemblies, with both inner and outer being round.
I don't know if this tells us anything or not, but it's interesting nonetheless.

[ou1954]

Originally Posted by huafist

So, I just checked the RSAs in several of my guns:
Springfield XDm .45
Springfield XDm 9mm
Taurus PT24/7 Pro .40
SCCY CPX2 9mm
S&W Bodyguard .380

ALL of them have round wire springs.
The Taurus, SCCY, and, curiously, the Bodyguard all have dual spring assemblies, with both inner and outer being round.
I don't know if this tells us anything or not, but it's interesting nonetheless.

It's interesting and a learning experience. To clarify, would you agree that the Sd9VE has a "flat wire" recoil spring?

I just saw a video about a Glock and it seemed to have dual springs, flat wire. Of course there are lots of Glock models and I can't tell one from the other just by looking from a distance.

[huafist]

Originally Posted by ou1954

It's interesting and a learning experience. To clarify, would you agree that the Sd9VE has a "flat wire" recoil spring?

I just saw a video about a Glock and it seemed to have dual springs, flat wire. Of course there are lots of Glock models and I can't tell one from the other just by looking from a distance.

I would indeed agree the SD9VE spring is flat wire.

[ou1954]

Originally Posted by huafist

I would indeed agree the SD9VE spring is flat wire.

I just saw a video showing how to replace a stock S&W spring with a Wolff spring. The S&W OEM spring had the ends ground flat but the Wolff spring was just snipped.

I prefer a flat, finished, end on things like that. It exudes care and quality.

[OKFC05]

I can help you with some questions you have left unanswered.

1.

Does ISMI make the stock springs for S&W ?

Yes, but their sale is not restricted, so anybody can buy ISMI springs, including you and I.

2. Why does Wolf refer to FORCE as pounds of energy?
They just misspoke. In college we "ivory tower snob physicists" used to say "excuse them, they are engineers". A 16# spring for an M&P requires 16# of Force to pull the slide all the way back on that pistol.
Put a Glock spring in a S&W and the force required to pull the slide all the way back may be different because of different final length. Arbitrarily switching springs between brands/models is an empirical exercise (trial and error).
This usage is NOT consistent with the standard scientific way of measuring springs.

3..Why does each spring manufacturer insist THEIR springs are the best buy?
On come on, Ford is supposed to admit Chevy has better v8s??!!

The round wire springs are somewhat smoother initially, but the flat wounds are far superior in longevity: That's why flat wound springs are almost universally used where long life and high cycles are vital.
If you want to use round wire springs in your S&W and change them every 3K shots, go ahead and do so; they will work perfectly, as they have for 100 years in 1911s.

[huafist]

Originally Posted by ou1954

I just saw a video showing how to replace a stock S&W spring with a Wolff spring. The S&W OEM spring had the ends ground flat but the Wolff spring was just snipped.

I prefer a flat, finished, end on things like that. It exudes care and quality.

I agree. I would also expect a snipped end to gouge against it's capture surface, even if the edges are broken. I'd probably want to use a thin washer or the like between it and the capture to prevent wear.
But, then again, with no more spring pressure than we're talking here, it probably doesn't make much of a difference.

[huafist]

Originally Posted by OKFC05

The round wire springs are somewhat smoother initially, but the flat wounds are far superior in longevity: That's why flat springs are universally used for auto valve springs.
If you want to use round wire springs in your S&W and change them every 3K shots, go ahead and do so; they will work perfectly, as they have for 100 years in 1911s.

Ummm... I've built a LOT of engines over the years, ranging from 140cid I4's to 630cid big blocks, and I've never seen a flat spring used as a valve spring... they're always round.

[OKFC05]

Originally Posted by huafist

Ummm... I've built a LOT of engines over the years, ranging from 140cid I4's to 630cid big blocks, and I've never seen a flat spring used as a valve spring... they're always round.

Few people have seen how a Formula One engine is made. I changed this post just after I posted it when I realized ordinary car engines most people have seen are a poor example. I changed it to " That's why flat wound springs are almost universally used where long life and high cycles are vital. "

From ISMI: Our springs utilize the same design and manufacturing technology as used in IndyCar and Formula One racing. In a typical 500 mile race, a valve spring in an IndyCar will go through more than 2,500,000 compression cycles)

A "flat wound spring" is not the same as a "flat spring."
ISMI initially produced the flat wound silicon alloy springs for NASA and later sought commercial applications when NASA funding crashed. Fatigue tests have been run on the M&P's flat wound recoil springs and the results were, in test terminology, "Inconclusive." No spring ever failed, and after 100,000 shots, the tests were terminated.