Basics of the Steyr M series trigger system

Discussion in 'M, C, L and S Series' started by damyxz, May 25, 2010.

  1. damyxz

    damyxz New Member

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    I have been shooting the steyr m 40 for a while now, I got it used and the trigger is OK. I recently acquired a NIB M9-A1 and the trigger is gritty and heavy(compared to my other pistols) I have been studying the pistol and how it works and today I totally dis assembled the sub frame assembly and I was able to lighten the triggerto about 3.5 lbs of pull. So here are some explanation on how this pistol works.
    The whole firing sytem is an engineering marvel based on a type of sear called " falling block system" with a few modifications for incorporation of safety system. The firing pin catch(#10) rides on a pair of slot cut out on the sub frame(#6) and the lever(#11)is on a fixed pivot on the sub frame. The front end of the firing pin catch(10) rides on the top edge of the lever(11) during the cocked position in which the firing pin spring(46) pushes the firing pin catch and the lever forward. The striker(43) at this time is partially cocked.(The nub of the striker and the nub of the firing pin catch block are in contact at this point). When the trigger is pulled to fire, the trigger bar(16) transfers the movement to the firing pin catch(10) by pushing on a slot cut underneath the firing pin catch(10). This moves the firing pin catch(10), the lever(11) and the firing pinr(43) backward compressing the firing pin spring(46) towards full compression. The firing pin catch(10) continues to move rearward while the lever is stopped by the firing pin catch pi(14). The front end of the firing pin catch(10) disengages from the lever(11) causing the front end of the firing pin catch(10) to fall down, releasing the firing pin(43) and firing a round. The respective springs acting on each part mentioned returns everything to rest position(uncocked).

    To improve the trigger feel and the pull of the trigger, I polished the top of the lever(11), front part of the firing pin catch(10) and the top part of the firing pin to reduce the grittiness. I did not attempt to lessen any spring tension because the system runs on the correct balance of the springs. I also polished the insides of the slots for the firing pin catch and the contact surfaces for the trigger bar. Another thing that might reduce the trigger pull is if you can make the angles of the firing pin nub and the firing pin catch nub(I better leave this alone) or maybe reduce the firing pin spring tension. Just polishing the mentioned areas gave me a smotther and better trigger pull. I hope this helps anybody with this type of pistol.
     
  2. bigtaco

    bigtaco Active Member

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    sounds about right to me, though i've never seen polishing alone get to 3.5 pounds.

    https://www.steyrclub.com/vb/downloads.php?do=cat&id=2

    the biggest improvement in trigger pull, and one you did not mention, comes from polishing the striker spring guide rod. The weight travels with the sear and any friction between the weight and the rod is very apparent in the trigger pull.

    You can eliminate the metal/metal friction by replacing the weight with a Glide-Rite striker bushing available here:


    http://btguiderods.com/category/steyr-acc/

    Also available is an aftermarket striker spring that runs 100% IF you also bend spring #13 to 90 degrees.


    modifying the striker/sear engagement angles does nothing to affect trigger pull. the trigger bar is pushing the sear which is pushing the striker straight back. Rearward travel would be possible if the mating angle was 90 degrees. The angle only exists to allow the striker to pass over the sear and push it down once the sear has fallen off of the post.

    They're neat pistols and I think the design is very simple. The only thing that I really yearn for is a safe and effective under/over-travel stop. It would need to be incorporated into the trigger itself, which would thusly need to be made of metal because set screws in plastic are big time trouble. Machining a trigger with a trigger safety AND an over-travel stop is a tall order but maybe one day someone will get 'er done. Perhaps even raise the trigger bar pivot and knock another pound out of the trigger pull.
     

  3. damyxz

    damyxz New Member

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    I have not explored the firing pin spring guide rod friction yet. Changing the angle of the mating surfaces of the firing pin and the firing pin catch can reduce the downward force applied by the firing pin on the firing pin catch thus reducing the friction between the firing pin catch and the lever. Anyway, Thanks for the heads up on the firing pin guide rod, I think it is something else to look into.
     
  4. Syntax360

    Syntax360 Premium Member

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    You really ought to check out BT's delron cups while you're tinkering - they give the trigger a crispy, smooth break. :thumbsup:
     
  5. damyxz

    damyxz New Member

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    I am going to order the delron cups for the spring. Another thing I'm thinking of experimenting on is to lessen the firing pin spring tension a bit and also the lever spring. These two kinda works in balance. I might experiment and get a spare lever spring and firing pin spring later. Thanks for the suggestions.
     
  6. guitargeak99

    guitargeak99 New Member

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    Just what exactly are you guys using to polish the components of your Steyr
     
  7. damyxz

    damyxz New Member

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    I use a cordless dremel tool with a rubber polishing wheel first and then buff it with the cotton wheel with the polishing media. for the sub frame I use an armorer's polishing stone.
     
  8. guitargeak99

    guitargeak99 New Member

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    Great. looks like I'll be breaking out my dremel.
     
  9. revjen45

    revjen45 Member

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    Suggestion for over travel stop:
    A piece of pencil eraser of proper thickness superglued in behind the trigger. I haven't tried this with the Steyr, but it has worked on other guns.
    Yeah, I know it's Hillbilly engineering.
     
  10. Kalakov222

    Kalakov222 New Member

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    Hi, this link your posted (https://www.steyrclub.com/vb/downloads.php?do=cat&id=2) isnt working.

     
  11. Case

    Case Well-Known Member

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    There are more videos on the polishing.
    And how to help for triggers and Action working .

     
    Michael Dobesch likes this.
  12. Kalakov222

    Kalakov222 New Member

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    Thanks
     
    Case likes this.