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Anybody notice that someone from Chandler, AZ is offering a "magic" (his word) trigger lightening job for the FS2000? He is advertising it as just over 5 lbs pull. Wonder if he's replacing the springs? I had no knowledge of this prior to today, have no knowledge of what he is doing to achieve this "magic", and am not associated with him in any way, in case anyone is wondering.
This is the chandler person's webpage:

K&M Aerospace FN FS2000 K&M Lightning

If you notice he claims:You need to send me your hammer pack to do a bit of machine work on it and do my magic. It is not like the other modifications that I do to lighten the trigger as this one is not a DIY fix. I wish it was but its not.
It sounds like something a whole lot more drastic than spring changes. That's not to say new springs aren't involved, but I'd guess that it's more significant than that.
 

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Discussion Starter · #22 ·
This is the chandler person's webpage:

K&M Aerospace FN FS2000 K&M Lightning

If you notice he claims:You need to send me your hammer pack to do a bit of machine work on it and do my magic. It is not like the other modifications that I do to lighten the trigger as this one is not a DIY fix. I wish it was but its not.


It sounds like something a whole lot more drastic than spring changes. That's not to say new springs aren't involved, but I'd guess that it's more significant than that.
If anyone has a hammer group modified by K&M and is willing to post pictures, it would be interesting to see what's been done.
 

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Discussion Starter · #23 ·
I got two of these and the sear from purplenv and planned on t.rying to get it chromed if possible with a neu trigger to see if it helps with the trigger pull. The aluminum hammer looks just like the fs2000 hammer and is about the same weight add well, lookslike see good product. I will let you know how it turns out after I use it a few times.
I worry that aluminum may be too soft (depending on the alloy) and will deform eventually. Chroming it would help but I'd prefer a heavier steel hammer that would let me lighten the hammer springs and thus reduce friction with the sear, allowing heavier sear carriage springs. I am anxious to see how you fare with it, krider24.
 

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Discussion Starter · #24 · (Edited)
Third Spring Set Tests

Third round of tests. Numbers 1 and 2 are the original OEM Gen 1 and Gen 2 hammer packs. Number 3 is the “winner” from the first roundof tests.
The test bed modified hammer group is a Gen 2 as I could not bring myself to modify my only Gen 1 Hammer Group.

Spring #

1

2

3

21

22

23

24

25

26

27

28

OD (in)

0.260

0.260

0.300

0.240

0.296

0.300

0.300

0.240

0.240

0.300

0.300

ID (in)

0.196

0.196

0.240

0.192

0.236

0.248

0.248

0.196

0.196

0.256

0.256

Free Length (in)

1.125

1.125

1.130

1.250

1.250

1.130

1.250

1.130

1.250

1.130

1.250

Rate (lbs/in)

?

?

6.500

3.900

3.900

3.900

3.700

3.600

3.300

2.700

2.400

Max Load (lbs)

?

?

3.400

2.300

2.700

2.200

2.200

2.600

2.600

2.100

2.100

Solid Height (in)

0.481

0.481

0.290

0.300

0.540

0.230

0.240

0.240

0.260

0.170

0.190

Pull (lbs, oz)

8, 10

9, 9

6, 9

6, 4

6, 4

4, 10

5, 11

4, 15

5, 7

4, 7

4, 13

Note

1

2

3

3

5

3, 8

3

3, 8

3, 8

8, 9

8, 9

Notes:

1. Gen 1 Hammer Group, several hundred rounds, greased, Neu-Trigger installed, OEM springs
2. Gen 2 Hammer Group, new, no modifications, OEM springs
3. Solid height is short. When the sear carriage is compressed, the hammer could rotate sufficiently to lock against the bottom of the sear carriage
4. Solid height just long enough to prevent locking
5. Solid height OK
6. ID too small. Had to hand fit to find a pair that worked
7. Solid height is just short enough to release hammer
8. Hammer group butt strike on bench can cause hammer release
9. Spring is not strong enough to hold sear carriage forward against released hammer. Hammer flips forward and locks above base of sear carriage.

Looks like I've hit the bottom limit of the test group.

Now to evaluate for a "winner" to field test.

Thoughts, comments, suggestions, critiques welcome.
 

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Discussion Starter · #25 · (Edited)
Final Results (For Now...)

Evaluations and remaining candidates for lighter trigger pull spring sets (#1 and #2 retained for reference):

Spring set #3 was the winner from the first test set. #4 - #10 were all heavier pulls.
Spring sets #11 - #13 were too heavy.
Spring set #16 was too heavy.
Spring sets #20, #23, & #25 - #28 were too weak, allowing Hammer Group butt strike releases too easily.


Spring #

1

2

3

14

15

17

18

19

21

22

24

OD (in)

0.260

0.260

0.300

0.296

0.240

0.240

0.300

0.300

0.240

0.296

0.300

ID (in)

0.196

0.196

0.240

0.236

0.192

0.192

0.248

0.248

0.192

0.236

0.248

Free Length (in)

1.125

1.125

1.130

1.190

1.130

1.250

1.130

1.250

1.250

1.250

1.250

Rate (lbs/in)

?

?

6.500

5.000

4.900

4.600

4.600

4.300

3.900

3.900

3.700

Max Load (lbs)

?

?

3.400

3.400

3.400

3.400

3.300

3.300

2.300

2.700

2.200

Solid Height (in)

0.481

0.481

0.290

0.390

0.280

0.300

0.230

0.240

0.300

0.540

0.240

Pull (lbs, oz)

8, 10

9, 9

6, 7

6, 13

5, 10

6, 14

5, 14

6, 9

6, 4

6, 4

5, 11

Note

1

2

3

3

3

3

3

3

3

5

3

Notes:
1. Gen 1 Hammer Group, several hundred rounds, greased, Neu-Trigger installed, OEM springs
2. Gen 2 Hammer Group, new, no modifications, OEM springs
3. Solid height is short. When the sear carriage is compressed, the hammer could rotate sufficiently to lock against the bottom of the sear carriage
4. NA
5. Solid height OK

I eliminate spring sets #15, #18, and #24 to provide an additional margin above the highest pull spring set from which I could easily produce a butt strike release (#26 @ 5lb, 7oz).

I eliminate spring sets #14 and #17 since there are viable candidates at lower pulls.

Remaining spring sets and all known specs for each (reference OEM spring specs are directly measured, guessed at, or unknown)



Spring #

1

2

3

19

21

22

OD (in)

0.260

0.260

0.300

0.300

0.240

0.296

ID (in)

0.196

0.196

0.240

0.248

0.192

0.236

Free Length (in)

1.125

1.125

1.130

1.250

1.250

1.250

Rate (lbs/in)

?

?

6.500

4.300

3.900

3.900

Sugg. Max. Defl. (in)

?

?

0.520

0.770

0.590

0.710

Max Load (lbs)

?

?

3.400

3.300

2.300

2.700

Solid Height (in)

0.481

0.481

0.290

0.240

0.300

0.540

Wire Dia. (in)

0.032

0.032

0.030

0.026

0.024

0.030

Total Coils

~14

~14

9.750

9.380

12.400

18.000

Material

Music Wire?

Music Wire?

Stainless

Music Wire

Stainless

Music Wire

Ends

Closed Ground

Closed Ground

Closed Ground

Closed Ground

Closed Ground

Closed Ground

Finish

None?

None?

None

None

None

Gold Irridite

Pull (lbs, oz)

8, 10

9, 9

6, 7

6, 9

6, 4

6, 4

Note

1

2

3

3

3

5

Notes:
1. Gen 1 Hammer Group, several hundred rounds, greased, Neu-Trigger installed, OEM springs
2. Gen 2 Hammer Group, new, no modifications, OEM springs
3. Solid height is short. When the sear carriage is compressed, the hammer could rotate sufficiently to lock against the bottom of the sear carriage
4. NA
5. Solid height OK

This leaves 4 likely candidates in a fairly narrow pull range. For lack of any better criteria, I elect to go with spring set #22 as the lower pull and a Solid Height that is very close to the original springs.

Reinstalling spring set #22 in the test bed Hammer Group and performing an extended pull test produces an average 6 lb, 4oz pull, which agrees with the initial test.

Installing spring set #22 in a new test Gen 2 Hammer Group (the pins in the test bed Hammer Group are becoming loose in the test bed Hammer Group Boat after so many spring exchange test cycles) and performing an extended pull test with the Hammer Group lubricated produces a pull of 6 lb, 7 oz. It is not surprising that a new, never fired Hammer Group would have a slightly higher pull. Installing a Neu-Trigger and lubricating the mating surfaces gives an extended pull test average of 5 lb, 15 oz.

The feel of the trigger is fairly smooth with a barely noticeable 2 stage pull. There is almost no jerk / creep / twang as the trigger is pulled.

Field test results to follow.

As always, thoughts, comments, suggestions, and critiques welcome.

The happy family (Papa Gen 1, Momma Gen 2, the 3 little test units.)

Hammer Group Happy Family.jpg

 

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Gungineer said:
the pins in the test bed Hammer Group are becoming loose in the test bed Hammer Group Boat after so many spring exchange test cycles
Now you need someone to recreate the hammer group boat in aluminum, to allow extended test cycles! Overkill you say? :th_1087:
 

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Wouldn't using slightly lighter hammer springs reduce the friction making the trigger pull easier? Or would this cause a safety issue like the lighter springs on the carriage? I believe the Ps90 springs have a lighter tension.
 

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Discussion Starter · #28 ·
Now you need someone to recreate the hammer group boat in aluminum, to allow extended test cycles! Overkill you say? :th_1087:
The cost of that would buy a lot of Hammer Groups and the test bed isn't useless. The sear carriage pin has just gotten easy to push out which makes me uneasy about leaving it in the FS2000 long term. A little blue (or red) Loctite would probably solve that problem.
 

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Discussion Starter · #29 · (Edited)
Wouldn't using slightly lighter hammer springs reduce the friction making the trigger pull easier? Or would this cause a safety issue like the lighter springs on the carriage? I believe the Ps90 springs have a lighter tension.
Yes, a lighter hammer spring would reduce friction, as would a smoother metal / polymer (hammer / sear) or metal / metal (hammer / Neu-Trigger) interface. The two together (lighter spring & metal / metal interface) would produce a smoother and easier pull. You'd have to have both the heavier hammer and the lighter spring or you run the risk of light primer strikes (light hammer / weaker spring) or excessive primer strike (heavy hammer / strong spring). The hammer springs are very strong in order to give the very light hammer enough kinetic energy to (through the firing pin) reliably set off the primer. Theoretically it would reduce safety by some margin since reduced friction would mean less resistance to the sear moving back but it would be a fraction of the sear carriage spring force. The problem is that since the energy is directly proportional to the mass (or in this case rotational inertia) but proportional to the square of the rotational velocity, you have to quadruple the rotational inertia (RI) to be able to halve the rotational velocity (RV). Quadrupling (or more) the RI isn't that hard since the hammer is so light, but then you have to experiment with the springs to get half (or less) the RV. This is complicated by the fact that quadrupling (or more) the RI means the springs have to be stronger to overcome the higher inertia and get it up to half (or less) speed so it's not just cutting the spring force in half. Probably more like 70% at a guess. This all assumes I remember my physics correctly after 30+ years. Plus get the hammer super heavy and the springs very light and there starts to be a measurable delay between tripping the hammer and the primer igniting because of the time required to accelerate the heavy hammer. I don't know if that becomes a measurable problem at some point but it would probably be way outside any reasonable hammer / spring arrangement. So you either need a significant amount of calculation or you go through the same experimentation cycle I've been doing with the sear carriage springs and test for when you stop getting reliable primer ignition.:?:
 

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i just put the ps90 springs in a fs2000 pack with the aluminum hammer and will hopefully get time to take it to the range sometime this week to see if if fires reliably. the springs are definately lighter so this would more than likely fix your problem with the hammer pushing past the carriage. the aluminum hammer is 16g and the plastic hammer is 6g.
 

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Well I finally got around to testing the pack with the Ps90 springs and it would not fire the round, I gave it three strikes before switching back to a pack with normal fs springs and it worked fine. Next I will try one of each springs and see of that works.
 

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Discussion Starter · #33 ·
Well I finally got around to testing the pack with the Ps90 springs and it would not fire the round, I gave it three strikes before switching back to a pack with normal fs springs and it worked fine. Next I will try one of each springs and see of that works.
You may need to go through the same process I did with the carriage springs. Try springs with specs near what you estimate the originals are and then work your way down. With the increase in mass (16 / 6 or ~2.67x) and assuming the mass is distributed proportionately the same as in the original hammer, producing an equivalent ~2.67x increase in moment of inertia, you can reduce the angular velocity to 1/sqrt(2.67) = 1/1.63 or 61% of original rotational speed. You have to accelerate this heavier mass to 61% of original speed in the same rotational distance so the springs (I assume) need to be more than 61% as strong as the originals but my math isn't strong enough to work this out.
I know that another rifle system that had similar work done was perfected through trial and error, not mathematical precision.
 

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Was surfing GB and found HDD now has a all aluminum hammer for PS90/FS2000s.
And for stupid money for something no one needs, to fix a problem that doesn't exsist. Just sayin'
 
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Discussion Starter · #35 · (Edited)
And for stupid money for something no one needs, to fix a problem that doesn't exsist. Just sayin'

You may be right. The polymer hammer is high quality. The only reasons I can think of to replace a light polymer hammer are if the hammer is of poor quality or if the hammer / sear interface has high enough frictional forces that reducing the friction with a metal /polymer or metal / metal interface and reduced power hammer springs significantly improve trigger pull / feel.
This is exactly the case in the one rifle system I am familiar with that has had this done. The polymer hammer in that system is poorly formed and has an inconsistent firing pin strike face. The factory hammer spring is very powerful to compensate for the very light hammer and the hammer / sear interface is a gritty, compressed mess. The replacement stainless steel hammer is far superior (better tolerances, solid firing pin strike face, much smoother sear mating) and the reduced power hammer spring makes the trigger pull even better. The cost of this upgrade is a fair fraction of the cost of the gun but, in my (and others) opinion, demonstrably well worth it.

The high quality polymer parts in the FS2000 hammer group produce a pretty low friction interface and adding the Neu-Trigger provides a polymer / metal interface, with measurable results as shown in my tables above. The benefit / cost ratio is pretty high. I'd need to see proof that a metal hammer is a big enough source of improvement to justify the cost. I certainly wish krider24 well in testing this.
For me, I believe that changing the sear carriage springs is a much higher return investment for improved trigger pull / feel, the downside being the potential for a reduced safely factor. I should test this but can't bring myself to deliberately drop my FS2000 from 6 feet onto concrete.
 

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Discussion Starter · #36 ·
Well I finally got around to testing the pack with the Ps90 springs and it would not fire the round, I gave it three strikes before switching back to a pack with normal fs springs and it worked fine. Next I will try one of each springs and see of that works.
Are you able to publish some results, even with the failure to fire?
Was the feel of the trigger improved with the metal hammer?
Was there a noticeable difference in trigger feel with ps90 hammer springs vs. fs2000 hammer springs (with polymer and metal hammer)?
Did you take any trigger pull force measurements with the different combinations?
Since there was no firing with the PS90 springs, those measurements will give us an extreme bottom limit measurement of any improvement and help us judge if the cost is worth the benefit. I would be interested in comparing the metal hammer results to the Neu-Trigger results and then measuring with both metal hammer and Neu-Trigger together.
 

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Time sends to be my biggest issue right now. I am trying to wrap up a lot of things for work before I leave for vacation later this week. But if you want I could give you my pack with the aluminum hammer and springs to test? I don't have the knowledge or tools to do the testing you have but I can tell you the trigger pull was noticeably lighter with the Ps90 springs and the aluminum hammer. If you are interested in the pack pm me.
 

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Btw my next test was going to be the same but with one Ps90 and one fs2000 hammer spring. Figured I would spilt the difference.
 

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Discussion Starter · #40 · (Edited)
Aluminum Hammer Tests

Thanks to krider24 for sending me his FS2000 hammer pack with an aluminum hammer for testing. He also included a PS90 hammer and PS90 hammer springs.

I weighed the 3 hammers with my ancient balance beam scale. I can’t vouch for the absolute accuracy of the thing but it will give relative values.

PS90 – 7.9g (82.3% of the FS2000 hammer)
FS2000 (Gen 2) – 9.6g
Aluminum – 15.5g (161.5% of the FS2000 hammer)

Since the shapes of the hammers are essentially identical, the moments of inertia should be proportional to the weights and thus the rotational energies should be proportional (assuming the springs produce the same angular velocity despite the different moments of inertia).

I tried the 3 x 3 combination table below with his hammer pack, testing 3 5.56 rounds for each try. I used XM193 type cartridges.


Springs

Hammer

FS2000 (x2)

FS2000/PS90

PS90

Aluminum

3 / 3

3 / 3

3 / 3

FS2000

3 / 3

3 / 3

0 / 3

PS90

3 / 3

0 / 3

0 / 3

The FS2000 springs were able to fire rounds with all three hammers.

The mixed FS2000 & PS90 spring pair worked only with the heavier FS2000 and Aluminum hammers.

The PS90 springs worked only with the heavy Aluminum hammer.

As I started with a full 30 round magazine, I was left with 9 rounds with lightly dented primers and 3 unused rounds. I put the hammer pack together with the Aluminum hammer and the PS90 springs and tested with the 12 remaining rounds.

Of the 3 unused rounds, 2 of 3 fired.

Of the 3 rounds tested with the FS2000 hammer and PS90 springs, 2 of 3 fired.

Of the 3 rounds tested with the PS90 hammer and the PS90 springs, 3 of 3 fired.

Of the 3 rounds tested with the PS90 hammer and the mixed FS2000/PS90 springs, 2 of 3 fired.

Of those 12 rounds, I was left with 3 rounds, 1 with a single dented primer and 2 with twice dented primers. I retested the 3 remaining rounds.

Of those 3 rounds, the 1 with the once dented primer fired. The other 2 did not.

Of those 3 rounds, I was left with 2 rounds, both with thrice dented primers. I retested these 2 remaining rounds with a standard FS2000 hammer pack.

Of those 2 rounds, both fired.

From this limited number of rounds tested, it appears that the Aluminum hammer and the PS90 springs combination is on the low end of acceptable energy delivery, firing 10 of 15 attempts.

For comparison, with this XM193 type cartridge, I have had no Failures to Fire of successfully chambered rounds with a FS2000 hammer pack with a standard FS2000 hammer and hammer springs.

On the basis of this, I would say that the PS90 spring force is too low to reliably work with the Aluminum hammer, so pull test measurements with the PS90 springs will give more than the best possible reduction in pull force with the Aluminum hammer.

Performing a trigger pull test with this hammer pack (Aluminum hammer and PS 90 hammer springs) provides a trigger pull of 9lb. 9 oz. The original pull tests (see above) show a standard Gen 2 hammer pack with a pull of 9 lb. 9 oz., so there appears to be no reduction in pull force with reduced power hammer springs. This implies that the vast majority of pull force is caused by the sear carriage springs, which is corroborated by the previous tests.

I do not know how many rounds krider24 has put on the hammer. With the pull tests and some trigger feel tests, I put a little over 50 firing pin strikes on it.

The pictures below show the condition of the Aluminum hammer at this time. You can see that where the hammer strikes the firing pin, the coating is gone and bare metal is exposed. The coating is also gone from a good portionof the edges of the hammer’s strike face and other edges. Where the moving parts group strikes and rides the hammer strike face, there are signs of coating wear. The metal underneath may, or may not, be deforming.
Hammer Image 1.jpg Hammer Image 2.jpg Hammer Image 3.jpg Hammer Image 4.jpg

Given these results, I can’t say that I see any significant improvement from using this Aluminum hammer. A much heavier hammer, such as a steel hammer, would likely improve firing reliability with the PS90 hammer springs but given the results above, I speculate it would be unlikely to improve trigger pull force or feel beyond what Dr. Coffee’s Neu-Trigger provides and would, undoubtedly cost significantly more.

Thanks again to krider24 for trusting me with his hammer pack and materials so I could run the tests.

As always, comments / critiques / thoughts / feedback / suggestions welcome.
 
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