SU-22 trigger job

I'm doing my trigger job today, taking lots of pics.  

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]

 

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.   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!

 

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.

 

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!

 

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]

 

This was what my hammer spring looked like from the factory- not the same on both sides like it should be:

 

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.


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


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.


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

 

I polished the area of the hammer where it meets the sear:

 

That's it, other than the filing of the sear.

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

 

Video of trigger testing:
[ame]http://www.youtube.com/watch?v=h7yDvCIJplQ[/ame]

 

I wish I had a way to measure the difference. changing the trigger spring (not the hammer spring) made it feel a LOT better.

 

I really should do a step-by-step video... while it's still fresh in my mind

 

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 >

 

Updated thread to include re-assembly steps.

 

Video step-by-step added to first post, along with video of trigger results

 

Now I want to do a trigger job on my urban varmit killer, my Remington pump pellet gun