SU-22 trigger job

Discussion in 'SU-22' started by henktermaat, Aug 21, 2010.

  1. henktermaat

    henktermaat New Member

    228
    Dec 13, 2008
    I'm doing my trigger job today, taking lots of pics.  :cool:

    Note: I am standing on the shoulders of giants who have gone before. Here's the reference thread (SU-16):
    http://www.ktog.org/cgi-bin/yabb2/YaBB.pl?num=1141757737/22

    Video step-by-step: [ame]http://www.youtube.com/watch?v=Zu5k_YUsjv0[/ame]

    See the results of the trigger job: [ame]http://www.youtube.com/watch?v=SbjvSis3Jq8[/ame]
     
  2. Liberty4Ever

    Liberty4Ever Moderator Supporter

    May 19, 2006
    Lexington KY
    Good luck!

    Don't take off a significant portion of metal and create an unsafe condition with a semiautomatic rifle that can fire if the wind blows or it's jostled while sitting on the bench. Polish, only!

    Can't wait to hear the results.

    I wish you could take before and after measurements of the trigger pull force. It's way too easy to spend a couple of hours on something and say it went from eight pounds to two pounds, because that's how it honestly feels, when in reality, it went from seven pounds to five pounds.

    I'd like to do this job myself too, and your positive report will encourage me.

    Worst case, I just bought a lot of replacement parts from Kel-Tec. Almost all parts are available on KelTecWeapons.com. If you bugger up some part, the replacement isn't very expensive.
     

  3. henktermaat

    henktermaat New Member

    228
    Dec 13, 2008
    All done. I have no way of measuring, so I didn't. But, I did it in four stages:

    1) Polish only, followed by a test
    2) Take metal off the sear where it meets the hammer, reassemble, test
    3) Repeat step two, then test again
    4) Take out trigger spring tension a little, then test.

    Step 1 took me to a smooth, but still stiff and hard-to-break trigger. Basically like stock, but very smooth.

    Step 2 improved the break a little. I was being so conservative (what's new) that I took the sear to a flat knife sharpening stone, and worked it in circles on the stone for about 30 seconds, just to the point where I could see that it had removed the milling marks. Checked the angle often. Put it back together and was happy to see it helped some.

    Step 3: at this point I was an expert in taking it apart and putting it together and could do it in 5 minutes. So, I milled a hair more off the sear - another 30 seconds of circular grinding motion interrupted by frequent angle checks- in all dimensions. Put it back together, and was very happy with the result!  I did a drop test of sorts by re-assembling the stock, and bringing the butt down hard a few times onto my workbench. At this point I had the same stiff and long-ish smooth trigger pull, followed by a sweet break.

    Step 4: at this point I decided I wanted to take out that pull a little, to I took the trigger spring and basically flattened it. Put it together and WOW.  :D Perfect. Did a few more "drop tests" and called it done.

    And heeeere's the disclaimer:

    WARNING!
    WARNING!
    WARNING!

    Modifying your rifle is not recommended and can potentially make it UNSAFE! YOU are responsible for what you do to your rifle! I did not tell you to do a trigger job!
     
  4. henktermaat

    henktermaat New Member

    228
    Dec 13, 2008
    Notes on the PITA factor, important for anyone wanting to attempt this:

    If you're a mechanically-inclined person, the type who can fix things yourself, take things apart and put them back together, then you'll have no trouble. You'll know if this is you or not  ;)

    I didn't find it hard at all. I don't know if it's because I'm just very awesome, or very careful. I did take lots of pictures to refer back, and the first time I put it back together I had to double-check my photos. I do fit the description above as a mechanically-inclined person.

    I did not have to use a zip tie or tie of any sort to get it together.

    Bending a small hook in the hammer spring is a must for ease of putting it back together.

    Re-assembly step-by-step:

    1) place the hammer spring onto the hammer
    2) place the trigger spring on the trigger assembly
    3) lay the stock down in front of you in the same orientation as when you took it apart
    4) make sure the hammer post is in place on the stock
    5) take the hammer, orient it properly in your hand, and "compress" the side of the spring that goes down by rotating it in the same direction as the wind. All in your hand.
    6) slide the hammer and spring down onto the hammer pivot post.
    7) hook the compressed side of the spring (the down side) up over the plastic nub (with the hole in it, where the front trigger post goes). This will hold the downside of the spring into place.
    8) you should be able to let go. The hammer will be in it's extended position.
    9) Make sure the safety post is in place and oriented in the right direction as when you noted when you took this apart.
    10) take the trigger assembly and trigger spring in your hand and orient properly.
    11) Place the trigger assembly down into the stock, making sure the front post goes into the front hole and the rear portion and flat part of spring goes under the safety. Push it down all the way.
    12) Important: move the safety to "fire" position. The notches will hold it here against the trigger spring.
    13) Take the upper side of the hammer spring, wind it around once to bring in the tension, and hook the end over the post on the trigger. It should stay there if you put the little hooked bend in it. Now all parts are in their proper places.
    14) Take the other side of the stock and orient it properly. Line up everything as best you can and press down. Here's where it gets tricky: it won't just slide all the way onto the gun. press it as far as it will go.
    15) Pick up the stock (it should stay together) and look down into the gap above the hammer/trigger area. See the hammer pivot post doesn't line directly up with the corresponding hole in the stock due to spring tension?
    16) Take a small flat-blade screwdriver and apply pressure to one side of this post to line it up with the hole while squeezing the two sides of the stock together at this point. It should go into the hole, but the stock will not go together just yet.
    17) Look down into the gap again - now you see the same problem with the front post of the trigger assembly. This one is usually way out of whack.
    18) Take your small screwdriver again and push this post into place, being careful not to let the hammer spring slide off the post. You will probably have to manipulate the plastic trigger itself to get the whole thing to move into place.
    19) With that in place, cock the hammer. Now the two halves should completely, or almost completely slide together.
    20) You may have to manipulate the coils of the hammer spring to get it all the way together. They sometimes get in the way.
     
  5. henktermaat

    henktermaat New Member

    228
    Dec 13, 2008
    It was gritty when I took it apart. Here's some "Frame of reference" photos.

    Important note - the hammer spring has been "sprung" in these pictures.

    Click any image to enlarge!

    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]
     
  6. henktermaat

    henktermaat New Member

    228
    Dec 13, 2008
    Here's the parts you'll need to work on.

    Clockwise from top left:

    Hammer (142)

    Trigger Spring (182)

    Trigger Assembly
    Trigger (208)
    Trigger Block (140)
    Sear (144)
    Sear Spring (180) - inside
    Sear Spring Pin (145) - inside
    Trigger Axis (298)
    Sear Pin (280)

    Hammer Spring (178)

    These are my own made-up terms for these parts and might not be correct.
    [Correct Kel-Tec names added and part numbers in parentheses]

    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]
     
  7. henktermaat

    henktermaat New Member

    228
    Dec 13, 2008
    This was what my hammer spring looked like from the factory- not the same on both sides like it should be:
    [​IMG]
     
  8. henktermaat

    henktermaat New Member

    228
    Dec 13, 2008
    After taking the trigger assembly apart (just push out the two pins) I polished.

    First I hit the sides of the sear with 400-grit sandpaper, then followed it up with a buffing wheel on a Dremel with polishing compound.
    [​IMG]

    I polished both sides of the sear and the center of the pin that it rides on to a mirror finish.
    [​IMG]

    Then I cleaned it well and re-assembled the trigger assembly. Also, I bent the hammer spring into this shape.
    Note the trigger spring is not yet modified here. I did not get a photo of it- so just picture it bent so that it's flat and not angled at all.
    [​IMG]

    Trigger assembly after polishing and re-assembly:
    [ame]http://www.youtube.com/watch?v=tRxGfDeXjY4[/ame]
     
  9. henktermaat

    henktermaat New Member

    228
    Dec 13, 2008
    I polished the area of the hammer where it meets the sear:
    [​IMG]
    [​IMG]
     
  10. henktermaat

    henktermaat New Member

    228
    Dec 13, 2008
    That's it, other than the filing of the sear.

    Here's some more frame of reference photos with springs removed for clarity:

    [​IMG]
    [​IMG]
    [​IMG]
     
  11. Liberty4Ever

    Liberty4Ever Moderator Supporter

    May 19, 2006
    Lexington KY
    I'm definitely encouraged, and given that I have a PLR-16, SU-16 and SU-22 that all need the same trigger job, I'm definitely inclined to read up on the process and take the plunge. It's something I've wanted to learn to do for a long time. I'd like to do trigger jobs on my two SUB-2000s as well, but that's a slightly different matter.

    I have some spare trigger parts now, so I'd be inclined to experiment a bit, but always careful not to take off some metal that would be needed for safety. Your testing for an accidental discharge if jarred after doing the work was smart. I'll do that as well.

    If the SU-22 and PLR-22 need less force to ignite the rimfire cartridge, it looks like Kel-Tec could have lightened the trigger pull by reducing the spring tension, and make a smaller tip on the firing pin if needed to generate enough pressure. But that would probably prevent SU-22 stocks from swapping onto SU-16 rifles that need more energy to ignite the cernterfire 223 cartridge. The stock SU-22 trigger pull is heavy, and the firing pin crushes a relatively large area of the rim compared to other .22 LR rimfire weapons. It makes for very reliable ignition, but at the cost of a heavy trigger pull.

    I have a trigger pull gauge. When I get a round tuit, I'll do a trigger job on my SU-22 and measure before (7 pounds 0.5 ounces) and after... hopefully four pounds or less.
     
  12. henktermaat

    henktermaat New Member

    228
    Dec 13, 2008
    Video of trigger testing:
    [ame]http://www.youtube.com/watch?v=h7yDvCIJplQ[/ame]
     
  13. henktermaat

    henktermaat New Member

    228
    Dec 13, 2008
    I wish I had a way to measure the difference. changing the trigger spring (not the hammer spring) made it feel a LOT better.
     
  14. henktermaat

    henktermaat New Member

    228
    Dec 13, 2008
    I really should do a step-by-step video... while it's still fresh in my mind :cool:
     
  15. Liberty4Ever

    Liberty4Ever Moderator Supporter

    May 19, 2006
    Lexington KY
    I have a trigger pull gauge and I'll make before and after measurements.



    That could be a super cheap and easy trigger job? Blast it all out with polymer safe Powder Blast, use some of that super high-tech magic trigger grease (take your pick from several making spectacular claims), and bend the trigger spring until it's flat.



    I have three trigger jobs to do. Maybe I'll do the first one with a few iterations like you did to gain familiarity and sneak up on it, then make a step by step video of the process on the second one, and when I mess up that video, which is inevitable, probably involving self inflicted bloodshed, I can start over on a new video on the third trigger job.

    Thanks again for posting this... both from the technical and motivational perspective.  :cool:

    This thread is in the finest tradition of KTOG. [smiley=thumbsup.gif]
     
  16. henktermaat

    henktermaat New Member

    228
    Dec 13, 2008
    If you have three guns that need this, then you need to go for it :)

    Re: bloodshed: at one point the spring did fly off the peg under tension and gouged my thumb >:(
     
  17. henktermaat

    henktermaat New Member

    228
    Dec 13, 2008
    Updated thread to include re-assembly steps.
     
  18. henktermaat

    henktermaat New Member

    228
    Dec 13, 2008
    Video step-by-step added to first post, along with video of trigger results
     
  19. henktermaat

    henktermaat New Member

    228
    Dec 13, 2008
    Now I want to do a trigger job on my urban varmit killer, my Remington pump pellet gun :)
     
  20. Liberty4Ever

    Liberty4Ever Moderator Supporter

    May 19, 2006
    Lexington KY
    That's a super nice video! A picture is worth a thousand words, and for something like this, a video may be worth a thousand pictures.

    I noticed that you polished the outsides of the sear, but you didn't polish the mating surfaces on the inside of the trigger block?