yanici
US Veteran
I noticed something white packed into the trigger return spring when I installed the APEX Carry Kit in my Shield. Is it necessary? Will it deteriorate? Will it become a maintenance issue later on?
What's That Packed Inside The Trigger Return Spring?
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Fastbolt
Member
The white fiber insert inside the trigger spring is to help dampen the vibration of the recoil forces.
S&W adopted this idea for their trigger spring in the early days of their Sigma pistols. I remember being told in an armorer class back then that the spring would last longer with it inside the coils to help dampen shock due to recoil harmonics.
It will continue to work when it becomes dirty, but it shouldn't be saturated with solvents, oils, etc.
The recommended replacement interval for the trigger spring is 5,000 rounds, anyway.
S&W adopted this idea for their trigger spring in the early days of their Sigma pistols. I remember being told in an armorer class back then that the spring would last longer with it inside the coils to help dampen shock due to recoil harmonics.
It will continue to work when it becomes dirty, but it shouldn't be saturated with solvents, oils, etc.
The recommended replacement interval for the trigger spring is 5,000 rounds, anyway.
Only 5000 rounds for the S&W factory return spring is not much. Here's what APEX has to say about their return spring. [copied from their FAQ section]
************************************************
Q) How well does the Duty Rate Trigger Return Spring Hold up?
A) The Apex Duty Rate Trigger Return Spring was engineered for a service life of greater than 1,000,000 cycles. But that wasn't good enough for us, we wanted better for our customers. After fabrication, we had the springs Shot Peened to reduce stress and fatigue as well as maximize service life. Shot Peening a Coiled Extension spring like our Duty Rate Trigger Return Spring increases it's expected service life by a factor of 10x. Which means our spring has an expected rating of nearly 10,000,000 cycles.
You can find out more about the Shot Peening process at Metal Improvement | Shot Peening
************************************************
Q) How well does the Duty Rate Trigger Return Spring Hold up?
A) The Apex Duty Rate Trigger Return Spring was engineered for a service life of greater than 1,000,000 cycles. But that wasn't good enough for us, we wanted better for our customers. After fabrication, we had the springs Shot Peened to reduce stress and fatigue as well as maximize service life. Shot Peening a Coiled Extension spring like our Duty Rate Trigger Return Spring increases it's expected service life by a factor of 10x. Which means our spring has an expected rating of nearly 10,000,000 cycles.
You can find out more about the Shot Peening process at Metal Improvement | Shot Peening
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When the SIGMA first came out, one of the gun magazines wrote up an "endurance test" of sorts, which involved dunking the hot pistol into water to cool it down after repeated firings.
The water caused the little tampon to go south and the spring broke. The S&W factory rep who was present was pretty amazed after the first failure. The spring was replaced and the test continued, and when the second one broke, again in fairly short order, they did some more detailed inspection and found the tampon had gone missing.
This is one issue that S&W has apparently not chosen to address, other than to recommend frequent replacement. Note that the M&P has a tampon in the same spring.
I have no knowledge as to whether S&W has changed the material, but it looks like the same felt pad looking stuff from the early days of the SIGMA. This creates a real problem for the M&P and the SIGMA for serious military use as dunking is apparently used frequently. I note also that there are cleaning kits sold by Cylinder and Slide and others perhaps that involve submerging the pistol or revolver in a cleaning liquid (without grips, it seems) and this would surely be a problem for this system.
Just my thoughts, but if your entire pistol depends upon a felt-like tampon then I would say you would want to give that pistol a second look prior to adoption or, if adopted, you would want to not use the dunking method of cleaning or cooling - and you would want to make sure your pistol is not used around a waterway, such as a lake or river. Those limitations seem to disqualify the SIGMA, the SD Series and the M&P from Water Patrol or other uses in which exposure to water or dunking into any liquid might occur. It seems also that a wet tampon that stays put would be a real source of corrosion for the spring, which could also cause a failure.
I wonder if anyone has conducted a recent test. I have asked and S&W has not wished to discuss the material used for the tampon. Can't someone build a spring that does not require a tampon? 1911s and Glocks do not require tampons.
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Fastbolt
Member
I haven't compared the current trigger spring to that used in the early Sigma. That class was long ago & far away, and I've never owned a Sigma.
The current M&P trigger spring design looks as though the ends do a decent job of containing the fiber insert. (Tight coils at one end and a hook at the other end.) Not going to be doing a submersion test, though.
The fiber insert looks larger than I remember, too. Maybe they revised it along the way? Dunno. They've certainly done enough other continual revisions and improvements over the years.
A couple other considerations ...
The trigger bar design of the S&W guns puts the trigger spring at the front, directly underneath the chamber, closest to the shock of recoil ... (the .45 barrel received a clearance cut at the right side of the feedramp for the front of the trigger bar to clear it back about '08, BTW) ... and the front of the spring itself is captured by the trigger pin. This puts the spring up close to generated recoil forces. This is unlike the Glock & Walther 99 designs, where the springs are located at the rearmost part of the trigger bars.
Also, "cycling" a spring upmty-ump times is one thing, but doing so when recoil forces/harmonics and shock are being transmitted to the spring, and acting upon the spring's material, may have a different effect, long term.
I remember in my first Glock class when the instructor and rep spoke of the firing pin and trigger coil springs as if they would run forever.
Later on, after my second Glock class, I received a wearable parts replacement schedule for .40's being used in LE, and both the firing pin and trigger coil spring were listed for recommended replacement at 5,000 rounds. I remember mentioning to a Glock employee that I'd received over 8K round service from a couple of trigger springs (different guns), and he said that was great.
I also received a letter (sent out to armorers) recommending that trigger springs be carefully checked for proper installation (someone did something wrong, somewhere, apparently
), as well as for cracks & damage to the springs, and that any springs other than the newest light grey finish ones be replaced with the new spring.
Later on, after yet another armorer class, I was told that the newest light grey trigger spring was now considered a lifetime spring. Of course, they've also revised the trigger bar so the hole for the spring is not only bigger, but the angle of the trigger bar at the spring engagement location has been changed to put less stress on the spring.
Who knows what I'll hear the next time in a Glock class?
Or, what other changes and revisions the S&W engineers may decide to incorporate at some point?
The current M&P trigger spring design looks as though the ends do a decent job of containing the fiber insert. (Tight coils at one end and a hook at the other end.) Not going to be doing a submersion test, though.
The fiber insert looks larger than I remember, too. Maybe they revised it along the way? Dunno. They've certainly done enough other continual revisions and improvements over the years.
A couple other considerations ...
The trigger bar design of the S&W guns puts the trigger spring at the front, directly underneath the chamber, closest to the shock of recoil ... (the .45 barrel received a clearance cut at the right side of the feedramp for the front of the trigger bar to clear it back about '08, BTW) ... and the front of the spring itself is captured by the trigger pin. This puts the spring up close to generated recoil forces. This is unlike the Glock & Walther 99 designs, where the springs are located at the rearmost part of the trigger bars.
Also, "cycling" a spring upmty-ump times is one thing, but doing so when recoil forces/harmonics and shock are being transmitted to the spring, and acting upon the spring's material, may have a different effect, long term.
I remember in my first Glock class when the instructor and rep spoke of the firing pin and trigger coil springs as if they would run forever.
Later on, after my second Glock class, I received a wearable parts replacement schedule for .40's being used in LE, and both the firing pin and trigger coil spring were listed for recommended replacement at 5,000 rounds. I remember mentioning to a Glock employee that I'd received over 8K round service from a couple of trigger springs (different guns), and he said that was great.
I also received a letter (sent out to armorers) recommending that trigger springs be carefully checked for proper installation (someone did something wrong, somewhere, apparently
), as well as for cracks & damage to the springs, and that any springs other than the newest light grey finish ones be replaced with the new spring. Later on, after yet another armorer class, I was told that the newest light grey trigger spring was now considered a lifetime spring. Of course, they've also revised the trigger bar so the hole for the spring is not only bigger, but the angle of the trigger bar at the spring engagement location has been changed to put less stress on the spring.
Who knows what I'll hear the next time in a Glock class?
Or, what other changes and revisions the S&W engineers may decide to incorporate at some point?
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isaidme1
Member
Was wondering this myself today. I picked up a used compact 9 with the tampon in the middle of the spring but my Fullsize 45 didnt have one. Strange!
Fastbolt
Member
Is it there, but blackened with powder fouling? Or, perhaps the aftermarket spring has been installed?
isaidme1
Member
Nope, it wasnt in my fullsize 45 out of the box. I bought that one new.
Fastbolt
Member
I'd call and tell them about it. Sounds like an oversight during assembly of the trigger bar (someone missed seeing the spring lacked its insert?).
CBStuard
Member
Next time can you start a new thread so I don't have to wade through 4 yr old stuff to get to the last post please?
ggibson511960
Member
Belt-and-Suspenders
That "tampon", polymer non-woven mesh, is obviously there to dampen trigger return spring vibration. During the forward stroke of the trigger to reset the mechanism, the trigger bar has been pushed out of engagement with the sear by a cam on the bottom of the slide. The trigger bar is loosely guided fore, aft and laterally in its firing cycle. Part of what keeps it in position is the tension of the trigger return spring. As the trigger strokes forward the spring load decreases and the trigger bar isn't guided as well until it snaps back under the sear, levered over by trigger return spring pressure. It all works readily in slow motion, but running at actual speed the bar could bounce sideways and not catch the sear. It doesn't look very likely if sufficient trigger return spring pressure is present, but the little buffer adds a margin of belt-and-suspenders reliability that S&W discovered in endurance testing. Stories from un-named gun magazine tests years ago don't hold much water.
I do have to wonder about fears of "fatigue" or "spring failure" from such a small deflection in its duty cycle. 5,000 cycles is nothing in the real metallurgical/mechanical world. S&W surely designed this thing for an infinite fatigue-limit life. Fatigue failure is incomprehensible. Creep rupture (inelastic failure) at the low service temperatures is also not credible. Simple corrosion is far more likely.
The buffer loads up with oil and unburned powder with age. My only concern would be with it impeding the movement of the trigger spring if it gets too gummed up.
That "tampon", polymer non-woven mesh, is obviously there to dampen trigger return spring vibration. During the forward stroke of the trigger to reset the mechanism, the trigger bar has been pushed out of engagement with the sear by a cam on the bottom of the slide. The trigger bar is loosely guided fore, aft and laterally in its firing cycle. Part of what keeps it in position is the tension of the trigger return spring. As the trigger strokes forward the spring load decreases and the trigger bar isn't guided as well until it snaps back under the sear, levered over by trigger return spring pressure. It all works readily in slow motion, but running at actual speed the bar could bounce sideways and not catch the sear. It doesn't look very likely if sufficient trigger return spring pressure is present, but the little buffer adds a margin of belt-and-suspenders reliability that S&W discovered in endurance testing. Stories from un-named gun magazine tests years ago don't hold much water.
I do have to wonder about fears of "fatigue" or "spring failure" from such a small deflection in its duty cycle. 5,000 cycles is nothing in the real metallurgical/mechanical world. S&W surely designed this thing for an infinite fatigue-limit life. Fatigue failure is incomprehensible. Creep rupture (inelastic failure) at the low service temperatures is also not credible. Simple corrosion is far more likely.
The buffer loads up with oil and unburned powder with age. My only concern would be with it impeding the movement of the trigger spring if it gets too gummed up.
