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Main spring effect on trigger pull, P-series

This is a discussion on Main spring effect on trigger pull, P-series within the SIG Sauer Gunsmithing forums, part of the SIG Sauer Forum category; I originally posted this on another forum a couple of months ago. I've learned some additional info since, corrections are preceded and followed by **. ...


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Old 01-10-2016, 10:37 PM   #1
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Main spring effect on trigger pull, P-series

I originally posted this on another forum a couple of months ago. I've learned some additional info since, corrections are preceded and followed by **.

Hammer or main spring strength, as we know, has a direct affect on trigger pull weight (nothing new there :c). With double action, or modifications of DA such as DAK, LEM etc, where the trigger is directly compressing the hammer spring for at least part of the cocking main spring compression, the spring strength's affect on trigger pull is significant. It's a mechanical thing, work (pulling the trigger) is being done through some manner of linkage and lever to compress the mainspring. In my tests below you can see this direct effect.

On the other hand, with SA the slide is doing the work of cocking the hammer fully, so the hammer spring strength affects trigger pull weight in a more indirect manner, mostly due to increased tension at the sear to hammer interface, as the sear blocks hammer "rotation" until the sear is released by pulling the trigger. Thus the effect of varying mainspring strength on SA trigger pull should be less. **I've seen a trigger pull reduction of up to 5 lbs after properly fitting a poorly fitted sear to hammer interface. This on a P938 that somehow escaped Sig factory with a trigger pull of over 12.5 lbs. I should note too, that a sear with a more positive angle cut will tent to exacerbate the ramp up of trigger pull to spring strength in SA, as it must slightly further cock the hammer and compress the main spring as the sear "cams" out of the hammer notch to release the hammer.**

So, to find out more, I did some testing with springs from Wolf and Gray Guns (GGI). ** Gray Guns told me thay purchase there main springs from Wolf, so the variations I observed are batch to batch variations in manufacturing. i.e. a spring may be labeled as 17 lbs, but the actual spring strength may vary a bit. In my tests, GGI means Wolf springs too - different batch.**

The test gun is a '99 vintage P229 DA/SA. I had previously done a trigger job on this gun, polishing internals and fitting sear to hammer. All trigger pull measurements listed are averages of 10 pulls each, all done in the same manner, holding gun stationary and pulling from mid point on the trigger, parallel and in line with slide, slowly increasing tension to break using a calibrated Lyman digital scale.

Prior to testing, I measured the installed length of a hammer spring on the test pistol, both "relaxed" and at full cock. The spring length at full cock measured 0.850".

I cobbled together a digital spring test stand using a SS draw rod. I made a hook on one end and threaded the other for a washer and nut to capture the spring. I passed the draw rod through a Delrin bench block held in a vise. And then used a digital scale (not the Lyman as it overloads at 12.5 lb) to pull the draw rod to compress the spring under test to the aforementioned 0.850" length. All three Wolf springs were close to their advertised strengths of 17, 18, and 19 pounds when compressed to a length of 0.850" (they were all about 3 or 4 ounces under their rated strength. They doubtless use a proper test rig - - so I'll call mine a little bit inaccurate - - but at least it seemed to be consistent.)

I only tested two samples of GGI's 17 lb springs **Same as Wolf, I'm guessing different batch**. Both of these springs measured just under 16 lbs on my test rig, a full pound under the Wolf 17 lb springs (this difference is also born out in the trigger pull numbers to follow).

Hammer springs were swapped out and both DA and SA trigger measurements made, no other changes were made to the test gun between spring swaps.

Wolf springs:

17 lb spring / DA 8 lb-11 oz / SA 3 lb-14.3 oz

18 lb spring / DA 9 lb- 1 oz / SA 4 lb- 2.6 oz

19 lb spring / DA 10 lb-.5 oz / SA 4 lb- 5.1 oz

(Note: you can see the trigger pull weight moving up in a non-linear fashion, with a much bigger jump from 18 to 19 than from 17 to 18 - no conclusion here, but I wonder if testing a 20 lb spring would have more dramatically increased trigger pull?)

GGI spring:

17 lb spring (measured as 16 lb.) / DA 8 lb-7 oz / SA 3 lb-13.5 oz

(Note: if you consider the GGI spring as 16 lb spring and plug it's numbers in ahead of the 17 lb Wolf, the even smaller step in trigger pull weights lends additional credence to the idea that DA trigger pull weight increases non-linearly and faster as hammer spring strength increases.)

I did one final "test" to confirm the Wolf and GGI 17 pound springs really were of different strengths. Using a Delrin plastic punch dropped down the barrel, I shot the rod out of the barrel with just the firing pin impact on the rod. The GGI 17 lb spring shot the rod approximately 3 feet high while the 17 lb Wolf spring shot the rod 8 to 12 inches higher in a half dozen tests each.

Please note that I am not saying GGI springs are of lesser quality than Wolf, or visa versa. I have no idea how they each "rate" their spring strength. I used a compressed length of 0.850" as that is what the spring measure on the gun AND that happened to be the length of compression that the Wolf springs were close to their rated weight.

After the tests, I installed an 18 lb Wolf spring in the gun.

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Last edited by bumper; 07-03-2016 at 07:12 AM.
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Old 01-16-2016, 03:13 AM   #2
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Why the 18 and not the 17?

Great post by the way!
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Old 01-16-2016, 03:41 AM   #3
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I'm sitting here early on a Saturday morning fondling my new P226 Legion thinking to myself, "How can I reduce the DA pull weight on this thing?" I mean, it is powerful enough to catapult rocks to the moon, I think.

Ten pounds...yowzers. I guess I'm a bit spoiled at this point by my Wilson Combat Beretta Brigadier Tactical, which has a reduced power mainspring (the D hammer spring).

And up pops your article, brother.

Wow, talk about a home run with a first post!

.

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Old 01-16-2016, 03:42 AM   #4
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BIG QUESTION TO/FOR ANYONE WHO HAS SWAPPED OUT THE MAINSPRING:

Have you experienced any light primer strike/fail to fire issues as a result?

.

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Old 01-16-2016, 10:00 PM   #5
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Quote:
Originally Posted by fishpick View Post
Why the 18 and not the 17?

Great post by the way!
Good question. I guess 'cause I'm a bit of a coward. 17 works, I tried it, no miss-fires, but the primer impression is a tadge shallower than with the 18. And I think Gray Guns recommends no weaker than 18 for carry, 17 for competition. That colored my decision making I guess.

I'm working on a new to me (and almost brand new) P226 SS Elite made in 2010. Going in it has a DA of 11.5 lbs and a SA pull of just over 5 lbs. Nothing like my P229 carry with smooth DA of just over 8 and SA 3.5. This P226 has all kinds of stiff and stagy stuff going on during the DA pull. I'll report back on how it turns out.
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Old 01-17-2016, 04:56 AM   #6
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Quote:
Originally Posted by Amsdorf View Post
BIG QUESTION TO/FOR ANYONE WHO HAS SWAPPED OUT THE MAINSPRING:

Have you experienced any light primer strike/fail to fire issues as a result?

.
Yes, but only with a 16 pound mainspring that was brand "X" and was over 18 months old. I don't remember where it came from.

Going to 18 or 19 solves the problem nicely but increases the trigger pull on my 220 DAO.
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Old 03-08-2018, 05:52 PM   #7
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I guess I never did report back on that P226 SSE

I did a full "bumper" action job on it. This is a German frame USA slide gun. The SS frame had small burrs and machine marks in the area of the hammer pivot and this was scratching the hammer and causing a fair amount of trigger roughness. So much for the vaunted "always good" German mfging. I cleaned up the frame roughness with flat diamond hones (as they fit nicely) and that came out as smooth as a baby's posterior.

Replaced short reach trigger with standard.
Reduced sear engagement angle.
Installed hammer pivot cam/spacer (similar to what Robert Burke installs but of my own design) to remove DA pre-travel.
Installed trigger over-travel.
Smoothed action.
SRT
Installed high lift safety lever of my design.

SA pull 3 lbs
DA pull 8 lbs
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Old 03-09-2018, 02:04 PM   #8
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So far, no light primer strikes using 17-lb mainsprings. But I only use them (along with the rest of the Gray Guns Master P-Series spring set) on competition guns. Various ammo from White Box to Blazer Brass to Freedom Remans.
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Old 03-09-2018, 02:58 PM   #9
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The 18 lb Wolff has been my go-to for all my classic P series pistols. The type of hammer strut set-up also has a great deal to do with the feel and staging of the pull in my opinion. I prefer the old long metal "4 piece" struts assembly with an 18 lb spring, but a 19 feels good to just a slight bit more stout. Problem is changing springs out if you want to, which is why I bought extra parts and pre-loaded several assemblies to swap in and out of different pistols. My second fave is the new "E2" short plastic base setup with the short 18 lb spring. Has a very nice even pull that feels like the old long base to me and much easier to change and test springs. Last is the long base plastic. Just don't like the way it stages and loads up toward the end. Could be my imagination, but that's the only one that counts.
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Old 03-09-2018, 03:06 PM   #10
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Quote:
Originally Posted by SIG Sauer Puss View Post
The 18 lb Wolff has been my go-to for all my classic P series pistols. The type of hammer strut set-up also has a great deal to do with the feel and staging of the pull in my opinion. I prefer the old long metal "4 piece" struts assembly with an 18 lb spring, but a 19 feels good to just a slight bit more stout. Problem is changing springs out if you want to, which is why I bought extra parts and pre-loaded several assemblies to swap in and out of different pistols. My second fave is the new "E2" short plastic base setup with the short 18 lb spring. Has a very nice even pull that feels like the old long base to me and much easier to change and test springs. Last is the long base plastic. Just don't like the way it stages and loads up toward the end. Could be my imagination, but that's the only one that counts.

I have noticed that, but never really attributed it to hammer spring assembly variations. I believe it is because the solid, 4-piece design was contained and lack of seat, so a more solid feel. The middle-era with the long seat would logically have more flex being longer plastic, while the E2 has more metal and less flex to deal with, although both have identical springs.

This is probably why I've recently decided to update all of my classic P's to the E2 style (also for future replacement parts availability).
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Old 03-09-2018, 03:46 PM   #11
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I also like the old long-strut/bracket type, but it is hard to fit under various grips. 18-lb spring is as low as I would go for anything that I would actually carry. I've also found the the 18-lb can sometimes feel lighter than a 17-lb spring because the 17-lb spring is actually longer than the 18, so it kinks a bit on the strut, whereas the shorter spring compresses more straight.
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Old 04-27-2018, 06:31 AM   #12
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Quote:
Originally Posted by bumper View Post
I guess I never did report back on that P226 SSE

I did a full "bumper" action job on it. This is a German frame USA slide gun. The SS frame had small burrs and machine marks in the area of the hammer pivot and this was scratching the hammer and causing a fair amount of trigger roughness. So much for the vaunted "always good" German mfging. I cleaned up the frame roughness with flat diamond hones (as they fit nicely) and that came out as smooth as a baby's posterior.

Replaced short reach trigger with standard.
Reduced sear engagement angle.
Installed hammer pivot cam/spacer (similar to what Robert Burke installs but of my own design) to remove DA pre-travel.
Installed trigger over-travel.
Smoothed action.
SRT
Installed high lift safety lever of my design.

SA pull 3 lbs
DA pull 8 lbs
Would you be able to post pictures on what exactly did u do to get such amazing results? Would love to try to replicate them!
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Old 04-27-2018, 07:03 AM   #13
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Have a 229 under the bed and a 226 for all my shooting. Both have the GGI hammer, sear and spring kits from GGI. I have the Wolff 18 lbs in both. The GGI 17lb would leave some lite primer strikes and ftf. No big deal except for the 229 under the bed. That one can never have a ftf. Top quality ammo would always work even with he 17lb. Most all the ammo worked good even with the 17lb. Some gun show reloads would ftf and some Freedom Munitions ammo would ftf. All the internals are polished to mirror finish and move with little effort. Guess if I used the 19lb it would have less ftf. But like the Freedom Munitions a lot and price is right. No ftf with Atlnata Arms, ASYM or other match ammo though.
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Old 04-27-2018, 09:50 AM   #14
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Quote:
Originally Posted by hitmissone View Post
Have a 229 under the bed and a 226 for all my shooting. Both have the GGI hammer, sear and spring kits from GGI. I have the Wolff 18 lbs in both. The GGI 17lb would leave some lite primer strikes and ftf. No big deal except for the 229 under the bed. That one can never have a ftf. Top quality ammo would always work even with he 17lb. Most all the ammo worked good even with the 17lb. Some gun show reloads would ftf and some Freedom Munitions ammo would ftf. All the internals are polished to mirror finish and move with little effort. Guess if I used the 19lb it would have less ftf. But like the Freedom Munitions a lot and price is right. No ftf with Atlnata Arms, ASYM or other match ammo though.
Then the problems with FTFs you are seeing coming from either primers that aren't fully seated or harder primers or both.

I solved that problem with one of my 220s by going to the 18 pound spring. I started with 16 pounds and had a few problems, then 17 pounds with the occasional problem, like 1/100, then no problems at all with 18 pounds.
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Old 04-28-2018, 05:10 AM   #15
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bumper,

Thank you for sharing all your data. Your posts are always well written and make sense to me. The sear angle as you mentioned can be a significant contributor to SA pull weight. My oldest SIG, a P229 ADxxxx seems to have less angle that the newer ones; driven by liability concerns I suppose?

On a couple revolvers I had used a triangular shaped ceramic stick from Brownells to stone a less-agressive angle on the hammer/sear. I clamped the part in a milling machine vice, with the surface to be stoned sticking above the vise jaws a couple thousandths, stoning down to the top of the jaws to keep things flat and perpendicular, etc. This seemed to work OK but I'd be interested in learning better methods/better tools to do this. I've seen for sale, fixtures for 1911s that allow checking the sear/hammer interface, and could see making one of those for working on my own SIGs.
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