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Thread: FNC trigger pull

  1. #1
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    FNC trigger pull

    I finally checked my trigger pull with a gauge. It was 11lbs! No wonder it's hard to squeeze the accuracy out of it. I was planning on sending it to Williams triggers in IL. but then read that he's closed after a fire.
    So I started researching it. I have a spring manufacturer nearby me that I'm going to for matching up springs and getting a series of lighter springs. I took off the trigger return spring and measured again and found the trigger to be a nice 5.5lbs.
    So I'm hoping with a lighter but still reliable trigger return spring alone it will get it to a reasonable pull. Other than the high pull weight it's clean, no "grittiness" or "hangs" just a clean break.I'll get part numbers for the springs and post them here as I go.
    I was also considering changing the hammer spring to minus 10% or so and keep checking for reliable ignition.
    I'm looking for some thoughts or other's experience with decreasing the hammer spring. Thanks

  2. #2
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    In the 80's the Belgian Army requested a high triggerpull. There whole shooting indoctrine was based on "prevent conscripts from shooting at all costs". So if a shot was fired, it should have been a calculated shot.
    In the 90's the finaly saw that shooting is an individual thing and they changed there methodes radicaly. No longer the NCO that calls in every shot. They got more faith in the soldier... (finaly) So yes, a 5 kilo pull is normal.

    The hammerspring indeed has serious influence on the triggerpull.
    If you open your FNC and pull the trigger dry. You see that the hammer moves against the hammerspring in.
    Keep all springs hard enough to keep the resets ok. So spring 542,555 and 557 have big influance.

    Changing out some triggerparts helps too. Some parts blend better to eachother as others. Polishing the contactsurface in the trigger-hammer connection gives it a more round AK47 trigger feeling.
    I sugguest you keep a spare set aside just in case you break something or you went 'to far".
    I got a 3 kilo triggerpull on the FNC i use for matches. Happy with it.
    The others, i leave as is for collection reasons.
    Paco



  3. #3
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    Awesome info, thank you! Do you have an estimate for the percentage spring force reduction possible on the mainspring without effecting reliable primer strikes? I was going to start at 10% less, then 15 and 20% less. Is that about right?

    Just an update=it looks like to have a spring manufacturer make one off springs is too expensive. So my next plan at least for the overpowered trigger return spring is to make my own. I've ordered several different thickness piano/music/spring wire and will wind it myself. Lots of how to on youtube. Whatever I come up with I'll post it here for anyone else that wants to do the same.

    Still working on the hammer spring options.
    I'll work on spring 555 last.
    Last edited by fnfncfan; 07-30-2020 at 03:04 PM.

  4. #4
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    Most easy step is to buy spare springs.

    Cut 1 winding, mount, try... And so on.
    If you went to far, take the spare spring and cut one less.

    If you need to make the springs custommade. You need to find out the "K" spring value. Newton/length compression ratio.
    Paco

  5. #5
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    I'm sorry it took so long to get to this, but here's the final results. As above with the hammer spring only, springs 555 and 557 removed, it was only a 5.5 lb pull.

    I started on spring 557. I bought 0.047 music wire from a hobby store. Wound it as close as I could to the original size with 5 windings on it. Cut the ends to match and matched the bends. It ended up 0.18 inside diameter. Major difference, however without changing spring 555 the trigger would not fully reset. 555 is a pretty standard shape and in my box of xtras I found one that worked perfect-little smaller inside diameter and lighter tension. It was OAL 0.53, wire diameter 0.025, inside diam. 0.132 and outside diam. 0.185. Not real important other than it fits and it's light enough tension to let the spring 557 fully reset the trigger. It was trial and error with a few springs before I got it.
    With the changes to springs 557 and 555 and the original hammer spring it comes in at 6.5 lbs trigger pull-huge difference!

    I then went to a spring manufacturer and bought a spring that was 10% lighter. It's not the wound wire of the original-looks to be same other than 2 windings shorter. With that in it's a perfect 5 1/4 lb. trigger. Now I just need to put some rounds thru it with the lighter hammer spring to make sure it hits all the primers hard enough, but with only minus 10% I don't anticipate any problems.

    The hardest part was having to try numerous diam. music wire and different number of windings with each.
    Well worth it!!!!

  6. #6
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    Has anyone looked at fitting a Geiselle Super Scar into an FNC? Elsewhere I have read of the similarities between the two, mostly in regard to using an FNC sear into a SCAR before the ATF nixed it, and it seems at least worth a look to determine the feasibility.

  7. #7
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    Quote Originally Posted by FN Around View Post
    Has anyone looked at fitting a Geiselle Super Scar into an FNC? Elsewhere I have read of the similarities between the two, mostly in regard to using an FNC sear into a SCAR before the ATF nixed it, and it seems at least worth a look to determine the feasibility.

    I looked into this also. In comparing blown up pics of available trigger group replacements it didn't look like anything would fit.

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