CZ Clone SAR K12 help with sear issues?

[TheChef1]

update: I figured it out. It was the pre travel screw out too far. It was fine with the slide off but with it on it didn’t work. 
 

 Mods Move to "other" if not allowed here but I figured since its a CZ/Tanfo Clone guys here would know whats up best. 

 

I got this inexpensive Sar K12 to mess around with a low budget LO build. Just got the slide back from being milled and with the slide on I seem to be having issues im assuming with sear engagement that are not present with the slide off. 

 

When I rack the slide the hammer goes back and stays back but doesn't seem to fully engage unless i give it a push back. This can be a very slight touch but it needs it to fully engage and set the trigger otherwise its just a dead trigger. 

 

The other issue is if I manually cocked the hammer it falls back forward probably 8 out of ten times. This does not happen when I have the slide off of the gun it cocks just fine. 

 

What I've done to the gun so far:

 

Slide:

-Just the cut. I have some more things I plan on doing but none yet. 

 

Frame:

-Blend the magwell to frame.

-Change trigger return spring

-Change to a Tanfoglio Extreme Flat trigger part# 30XTR00014B

-Change to a lighter galloway precision Mag Strut Spring

-Polish internals using Memphis mechanics video. Ive polished many other guns including Tanfo Stock 2 and a bunch of CZs. I using a Dremel with buffing pad and flitz.

 

My best guess is a took of material where I shouldn't have when I polishes but only using flitz and a buffing wheel ive never done this before. Click the links for videos of whats going on. Any help appreciated. No attempts to live fire the gun yet its brand new. 

Video 1: https://imgur.com/a/0Ue17sc

Video 2: https://imgur.com/a/SXMUiJm

 

Edited March 31 by TheChef1

[HesedTech]

1 hour ago, TheChef1 said:

What I've done to the gun so far:

I looked at your pic and video.

 

Several possibilities;

1. With the slide on your milling may have somehow interfered with the trigger bar. Are screws sticking down in under the slide?
2. The new trigger may have changed the ratio of the bar movement and you just aren't getting it to come back properly and push the sear up.
3. If you changed the slide bar lift spring to a lighter one it may not be pushing the bar up sufficiently.
4. If you took off too much material from the slide bar lobes (on top) you may have cause some issues.
5. Did you check the forward trigger stop screw? If the trigger is too far back it may do what you posted.
6. If the forward trigger stop screw is completely back and the trigger is resting against the frame you will have to trim the front of the trigger down to allow for proper forward movement.

From your pics it's hard to actually diagnose the issue. What I recommend is you reinstall the factory trigger and see if that resolves the issue.

Next run the gun without the optic and plate mounted to the gun.

Basically go back to stock and add things to see if the problem stops and then reoccurs.

 

Hope this helps, there are rarely true drop in parts. The fun and joy is in making an idea work.

 

 

[TheChef1]

3 hours ago, HesedTech said:

I looked at your pic and video.

 

Several possibilities;

1. With the slide on your milling may have somehow interfered with the trigger bar. Are screws sticking down in under the slide?
2. The new trigger may have changed the ratio of the bar movement and you just aren't getting it to come back properly and push the sear up.
3. If you changed the slide bar lift spring to a lighter one it may not be pushing the bar up sufficiently.
4. If you took off too much material from the slide bar lobes (on top) you may have cause some issues.
5. Did you check the forward trigger stop screw? If the trigger is too far back it may do what you posted.
6. If the forward trigger stop screw is completely back and the trigger is resting against the frame you will have to trim the front of the trigger down to allow for proper forward movement.

From your pics it's hard to actually diagnose the issue. What I recommend is you reinstall the factory trigger and see if that resolves the issue.

Next run the gun without the optic and plate mounted to the gun.

Basically go back to stock and add things to see if the problem stops and then reoccurs.

 

Hope this helps, there are rarely true drop in parts. The fun and joy is in making an idea work.

 

 

Hey man thanks for the response. I was thinking more about what it could be and thought about the pre travel screw. At first I thought the over travel screw was the issue but after adjusting it didn’t help. Sitting on the couch I realized I didn’t adjust the pre travel screw. Adjusted it all the way out and bingo we seem to be good to go. Will try to get it to the range tomorrow and see how it goes.

[HesedTech]

3 hours ago, TheChef1 said:

Hey man thanks for the response.

You bet. Glad it worked out.

 

Because of the price I considered buying one to see if it could be tuned to a nice running USPSA gun. Checked with Patriot Defense about milling for a direct mount SRO optic and it turns out the slide is too narrow. 

 

It does look good though, let the forum know how it works out for you.

Edited March 31 by HesedTech

[TheChef1]

4 hours ago, HesedTech said:

You bet. Glad it worked out.

 

Because of the price I considered buying one to see if it could be tuned to a nice running USPSA gun. Checked with Patriot Defense about milling for a direct mount SRO optic and it turns out the slide is too narrow. 

 

It does look good though, let the forum know how it works out for you.

Yeah they can’t do a direct mill unfortunately. I went with gun cuts. They made a plate for it for RMR footprint. It’s not as deep as I’d like but that’s ok. 
 

I plan to shoot it tomorrow side by side with one of my shadow 2s. I’ll let you know how it goes. 
 

here’s how it sits with an SRO 

[Seakphotog]

On 3/31/2024 at 7:45 AM, HesedTech said:

I looked at your pic and video.

 

Several possibilities;

1. With the slide on your milling may have somehow interfered with the trigger bar. Are screws sticking down in under the slide?
2. The new trigger may have changed the ratio of the bar movement and you just aren't getting it to come back properly and push the sear up.
3. If you changed the slide bar lift spring to a lighter one it may not be pushing the bar up sufficiently.
4. If you took off too much material from the slide bar lobes (on top) you may have cause some issues.
5. Did you check the forward trigger stop screw? If the trigger is too far back it may do what you posted.
6. If the forward trigger stop screw is completely back and the trigger is resting against the frame you will have to trim the front of the trigger down to allow for proper forward movement.

From your pics it's hard to actually diagnose the issue. What I recommend is you reinstall the factory trigger and see if that resolves the issue.

Next run the gun without the optic and plate mounted to the gun.

Basically go back to stock and add things to see if the problem stops and then reoccurs.

 

Hope this helps, there are rarely true drop in parts. The fun and joy is in making an idea work.

 

 

This was a terrific response!  I was going to suggest some but not all of that.  My immediate thought was the trigger screws. Looks like that was a simple fix.

[Seakphotog]

On 3/31/2024 at 11:44 AM, TheChef1 said:

Hey man thanks for the response. I was thinking more about what it could be and thought about the pre travel screw. At first I thought the over travel screw was the issue but after adjusting it didn’t help. Sitting on the couch I realized I didn’t adjust the pre travel screw. Adjusted it all the way out and bingo we seem to be good to go. Will try to get it to the range tomorrow and see how it goes.

Glad it was a simple fix!  Remember to loctite the screws.

[TheChef1]

4 hours ago, Seakphotog said:

Glad it was a simple fix!  Remember to loctite the screws.

Yeah Me too. Im just going to remove the pretravel screw and I did locktight the overtravel screw but I want to find a lnger one because it seems like its only hanging on by a couple threads

 

[Seakphotog]

23 minutes ago, TheChef1 said:

Yeah Me too. Im just going to remove the pretravel screw and I did locktight the overtravel screw but I want to find a lnger one because it seems like its only hanging on by a couple threads

 

Don't blame you - it does look like it's sticking pretty far out of the trigger.

[TheChef1]

Yeah its way out there