CZ Tuning 101 with Professor Atlas

[kneelingatlas]

There are no DA hooks on the hammer (the second set of hooks are the half-cock hooks), the 'hooks' for DA are on the disco and the trigger bar. I made this diagram back when everyone started talking about SRTS; they're pretty intuitive, so everyone seems to be using similar terms:

The DA shot breaks when the disco lifts up and the hooks on the front of the wings slip off the trigger bar. In SA where the back of the wedge catches the trigger bar is determines the trigger position when your finger is off the trigger so if the wedge is too wide (as in the gunsmith fit version) the trigger will not reset in SA mode. I knew if I ground down the wedge until it reset, I would still have slack in the FPB lifter before the trigger bar contacted the sear to release the hammer, so I ground the 'foot' of the FPB lifter and the corresponding spot on the trigger bar where it resets. I had no idea how much to take off, so I guessed and by chance it ended up perfect just remember it's easy to take off more metal, much harder to put it back...

This is why I put this part in the 'advanced' section
 

Edited July 12, 2017 by kneelingatlas

[Feralshooter]

Disco lifts up? I hate to disagree with Atlas, but doesn't the sear cage cause the trigger bar to drop, slipping off the bottom of the wings and releasing the disco?

I only make the distinction as this is important if you need to tune the DA break point.

[kneelingatlas]

Disco lifts up? I hate to disagree with Atlas, but doesn't the sear cage cause the trigger bar to drop, slipping off the bottom of the wings and releasing the disco?

I only make the distinction as this is important if you need to tune the DA break point.

My mistake, you're absolutely right

[Feralshooter]

Whew. I was hoping you wouldn't take offense professor.

Cheers (on my phone so can't use smileys)

[RaylanGivens]

Thanks for the pictures and explanations, kneelingatlas and Feralshooter... I was originally way off the mark, but have done quite a bit of reading (and re-reading) and taking my SP-01 apart over the last few days. I do have a few more questions...

So you (kneelingatlas) took half the amount necessary from the FPB lifter arm and the other half from the corresponding spot on the trigger bar. I assume you did it that way (half and half) to keep the alignment the same?

If the hammer is cocked on the SA hooks, pulling the trigger pushes the trigger bar back and that rotates the sear so that it slips out of the hammer hook and the gun fires.

When the hammer is down, pulling the trigger moves the trigger bar back which rotates the sear again, but does nothing because the hammer is down... The hammer hooks are not involved in a DA pull because the sear is already rotated above them when the hammer is released... So the real "timing" of the DA action involves making sure the sear is clear of the hammer hooks when the hammer is released.

I am having a bit of trouble understanding how the sear cage pushes down on the trigger bar. I understand that pushing the trigger bar below the disconnector "hooks" would cause the trigger to drop, but I can't figure out how the sear cage actually pushes the trigger bar down. Is the sear cage positioned in the frame on an angle so that it just naturally pushes down on the trigger bar when it is pushed back?

[Feralshooter]

You're about spot on RG. The only thing I'm not sure about is the part in the DA pull where the sear is lifted out of the way of the hooks first.

If you listen during the DA pull, you will hear the sear slip over the half cock notch, so at this point the sear has not been contacted by the trigger bar. My understanding is that the DA break point needs to be set so it is just before the hammer rolls back enough for the sear to catch the hooks. By this point in trigger travel the trigger bar is beginning to bear on the sear - enough so it will clear the half cock notch once the shot breaks.

If the DA is too advanced the sear may not be lifted yet, and the hammer will fall before really compressing the main spring, causing light strikes or no strikes if the sear catches the half cock. You would shorten the leg or wedge of the disco, effectively lowering the hooks to delay the DA break.

If the DA is retarded, the gun could fall into SA mode (as in the sear could catch the hammer), and you would need to pull the trigger again for it to fire. Stoning the underside of the wings or ears would effectively raise their height and allow the DA to break sooner.

The above I'm not 100% sure of though.

You are right about the trigger bar being pushed down. If you look at the side profile of the trigger bar, it is ramped a bit on the top surface. The underside of the sear cage is also ramped. The interaction of these 2 surfaces causes the trigger bar to dive as it is pushed to the rear.

When the slide cycles, the trigger bar ears that poke up past the top of the frame are depressed by the cycling slide (see the little cut outs on both slide rails that the ears rest in?) causing the trigger bar to be pushed even lower, out of contact with the sear. This allows the sear to reset. Try holding the trigger all the way to the rear and try to cock the hammer. It won't work as the TB is holding the sear up. Rack the slide and the TB is disengaged so the trigger resets.

Lots of rambling there. Hope it makes sense.

[Friction]

Lastly, here's another good resource for doing a detail strip. More pictures, but some slight variations because Oleg is working on a Shadow.

http://www.olegnikitin.com/news/complete-disassembly-assembly-of-cz-75-sp-01-shadow

This is a way better link than the same version with all the text in Russian. Thanks to whoever translated all of that.

[Friction]

There are no DA hooks on the hammer (the second set of hooks are the half-cock hooks), the 'hooks' for DA are on the disco and the trigger bar. I made this diagram back when everyone started talking about SRTS; they're pretty intuitive, so everyone seems to be using similar terms:

The DA shot breaks when the disco lifts up and the hooks on the front of the wings slip off the trigger bar. In SA where the back of the wedge catches the trigger bar is determines the trigger position when your finger is off the trigger so if the wedge is too wide (as in the gunsmith fit version) the trigger will not reset in SA mode. I knew if I ground down the wedge until it reset, I would still have slack in the FPB lifter before the trigger bar contacted the sear to release the hammer, so I ground the 'foot' of the FPB lifter and the corresponding spot on the trigger bar where it resets. I had no idea how much to take off, so I guessed and by chance it ended up perfect just remember it's easy to take off more metal, much harder to put it back...

This is why I put this part in the 'advanced' section

What parts of the disco should be polished, if any? I couldn't tell from the pictures in post #10 that included the hammer and disco but since this picture includes the names of the parts I figured this would make for a better reference. I talking specifically about a pre-B disco that will be installed in a Shadow if that makes a difference.

Thanks for putting this together.

[kneelingatlas]

The reason I didn't show any pictures polishing the disco is because I used the CGW disco which comes smooth as glass:

Since the factory discos are rough I recommend hitting the top of the wings where the rub on the sear cage, the bottom edge of the hooks and the pin hole.

[kneelingatlas]

Thanks for putting this together.

My pleasure

[schmeky]

kneelingatlas,

I just happened on this thread. I am more than impressed. Great job and I am glad someone took the (considerable) time and effort to put this together. I have saved this in my favorites and will forward to those that request such info, and I get many requests every day. Dr. Atlas indeed

David

Cajun Gun Works

[Friction]

So I just installed a Pre-B Disco on my Shadow target and everything seems to function fine timing wise except the safety in double action.

With the hammer fully forward and the safety engaged, if I pull the trigger it gets rough towards the back of the pull but if I keep going the hammer will fall (i.e. the gun just fired)

With the hammer fully cocked, if I engage the safety the hammer has about 2mm of movement before it hits a hard stop and prevent release of the hammer.

I believe this is what the Tang-Fo's do but the Shadows should not.

Any thoughts?

[Friction]

pics of pre-B Disco on Left and one removed from Shadow Target on right if anyone is curious about the shape difference or if it helps determine the issue causing the condition I mentioned above.

[trgt]

So I just installed a Pre-B Disco on my Shadow target and everything seems to function fine timing wise except the safety in double action.

With the hammer fully forward and the safety engaged, if I pull the trigger it gets rough towards the back of the pull but if I keep going the hammer will fall (i.e. the gun just fired)

With the hammer fully cocked, if I engage the safety the hammer has about 2mm of movement before it hits a hard stop and prevent release of the hammer.

My understanding is that the CZ safety only designed for hammer fully cocked? Hammer forward the safety should not be engaged?

http://www.brianenos.com/forums/index.php?showtopic=186846

[SpankYa]

Funny you should say that. My SP-01 with competition hammer has a safety that will not operate with the hammer down. My SP-01 Shadow with a competition hammer (both guns tuned by CZ Custom) allows me to actuate the safety up and down when the hammer is down. i don't think it is supposed to.

So I just installed a Pre-B Disco on my Shadow target and everything seems to function fine timing wise except the safety in double action.

With the hammer fully forward and the safety engaged, if I pull the trigger it gets rough towards the back of the pull but if I keep going the hammer will fall (i.e. the gun just fired)

With the hammer fully cocked, if I engage the safety the hammer has about 2mm of movement before it hits a hard stop and prevent release of the hammer.

My understanding is that the CZ safety only designed for hammer fully cocked? Hammer forward the safety should not be engaged?

http://www.brianenos.com/forums/index.php?showtopic=186846

[thompsoncustom]

Very good walk through. I've been wanting to see if I could get the double action below 3lbs but haven't had the time to try it yet lowest I've got DA so far was mid 3's with a 8.5lb hammer spring.

Edited April 30, 2014 by thompsoncustom

[kneelingatlas]

lowest I've got DA so far was mid 3's with a 8.5lb hammer spring.

Really? Which hammer are you using? I've gotten under 2# with the comp hammer and 11.5# spring.

[thompsoncustom]

Are we talking about the same action? If so you must tell me your secerts for a Sub 2lb DA

[kneelingatlas]

Oh, you said Double Action!?!

Clearly I misread, I thought you said you were having a hard time getting the SA under 3#.

A DA under 5# feels too mushy to me so I haven't even tried going lower than that.

How does it feel at three?

[Friction]

I'm not sure if this techniques is better or worse then using sandpaper but its what I used with this gun and with others since i am always paranoid about taking off to much metal when polishing.

I just smear the rubbing/polishing compound on a pipe cleaner and then just work it back and forth though the hole I want to polished and it seems to have the effect I'm looking for. It takes longer than I assume sandpaper would but for me it is worth the extra time.

[thompsoncustom]

I think the DA at that weight is great but you give up the crisp SA, can't have the best of both worlds.

[kneelingatlas]

kneelingatlas,

I just happened on this thread. I am more than impressed. Great job and I am glad someone took the (considerable) time and effort to put this together. I have saved this in my favorites and will forward to those that request such info, and I get many requests every day. Dr. Atlas indeed

David

Cajun Gun Works

Thank you David that means a lot coming from you, I really like using your products.

[emjei]

I think a 5.5 DA is perfect and Prod Legal....SA is very crisp also

. Thanks CGW I have that !!!

Sent from my SAMSUNG-SGH-I727 using Tapatalk 2

[kneelingatlas]

5.5 DA

Shadow or SP-01?

[thompsoncustom]

I don't think there is a to light DA only SA. I mostly run a 13lb main spring as I rather have a better SA than DA but I think if they were both around 3 lbs give or take that would be ideal.

Something like a 2.5 SA and a 4 DA sounds great

Edited April 30, 2014 by thompsoncustom