Question about break timing in DA/SA

[Aenimated1]

Sirs and Madams,
I am new CZs and the CZ forum. I am a big Sig Sauer fan and am just now warming up to the fine CZ pistols. I am fairly accomplished at action enhancement/tuning on the Sig side but now I want to work with CZs. I have my first victim...er...client who has supplied me with his CZ85. I like this pistol. I do however want to make the action better. I have already done most of the polishing and such that I can do. I am pleased with the results. BIG thanks to all the fantastic posters in this section.

My question is thus: I have read a few threads from some competent posters that detail the order in which actions are accomplished as you pull the trigger. Double Pedro has a fantastic thread about this subject. They state clearly that the DA break should be earlier in the pull than the SA break by about .03". On this pistol it is in the reverse order. The SA breaks clearly before the DA does. I found this to be the case before I even stripped this pistol. This specific pistol has a built in overtravel stop on the trigger. Right when I got the pistol I adjusted the overtravel to stop the trigger right after the SA shot. As it turns out this is not enough travel to let the DA break. So I let out the overtravel stop a bit and it stops right after the DA break but not so much after the SA.

What is the best course of action to fix this? I would prefer to have the timing such that the DA breaks before the SA but no more than the allotted .03".
For what it is worth this pistol has no FPB and I will be installing a new competition hammer this afternoon.

Robert

[Aenimated1]

To be more specific, I would like to simply move the DA break slightly ahead in the stroke. I think about .03" should be enough to accomplish this. I see there are atleast two ways to go about it. I would like to know which one is more preferable and why.

[Aenimated1]

After rereading the first post I meant to say "fairly adept" instead of "fairly accomplished". I think that made me sound like a stuck up douche :'(

[double pedro]

Robert - Welcome to the Forum and to CZs. 

Regarding timing of the DA and SA: If the DA breaks later in the trigger pull than the SA, you may get a problem where the SA releases the hammer, but the disconnector (responsible for the DA break) doesn't clear the trigger bar.  I would expect you would have this problem for the case you describe where the over travel stop set for SA doesn't allow the DA to break.  An obvious symptom of this is if you break the SA very gently, you can release the SA and lower the hammer by releasing the trigger (if that makes sense) - here is a recent link.  This may not always be the case if the SA hammer drops with enough force (and there is enough internnal play) that the disconnector bounces past the engagement of the trigger bar.  In this case, you are probably not getting as good of a hammer strike to the firing pin as you otherwise would.

To fix this, you can do one of two things, either delay the SA break (which can be done by removing material on the front surface of the lower leg of the sear where the trigger bar enagages it), or advancing the DA.  I think the most common way to advance the DA, is to effectively remove material from the underside of the disconnetor "wings".  There are two ways to do this - you can physically remove material from the undersides of each wing (making their entire vertical thickness less), or you can bevel the underside leading edge of the wings (the area that engages the trigger bar during the DA pull) - see photos in link above.

To decide whether you delay the SA or advance the DA, you may want to consider where each is breaking with the trigger pull, how much over-travel stop you have, how far the hammer is being cocked in DA, etc.  In the end it may not matter.  In either case, you probably only have to remove a small amount of material (a few 0.001"), so do a littel, re-assemble, check progress, repeat as necessary.

One final point, the measurements you reference from one of my old posts were representative of one particular pistol.  There is nothing essential about the 0.03" - it could be a little more or a little less as long as the DA breaks after setting the over-travel stop for SA, IMO.

P.S.  If you decide to advance the DA, I'd be inclined to remove material from the underside of the wings if it is fairly obvious that the DA breaks later than the SA.  This would better ensure that the disconnector actually clears the trigger bar when the SA breaks, rather than just bouncing off of it (as it currently seems to be doing).
 

[Aenimated1]

 Double,
Thank you so much. That is exactly the info I was looking for. If you ever happen to need help with a Sig Sauer do not hesitate to enlist me.
Also, I just took the above mentioned CZ to the range and it fired flawlessly. Accuracy is very good. I am just being picky about each mode (DA and SA) because it is fun for me.
Im sure you feel the same way.
I will let you know how the modifications go.
Thanks again,

Robert

[Stuart]

delay the SA break (which can be done by removing material on the front surface of the lower leg of the sear where the trigger bar enagages it)

DP..thanks again..hadn't thought of delaying the SA break..appreciate that information..

[double pedro]

Aenimated1 - Glad I could help out.  I look forward to hearing how everything goes.  There's a great deal of good information here that you seem quite able to put to good use.

eerw - No problem.  Always nice to be able to pay back for the many tips you pass along.

[Aenimated1]

Double,
I performed the modification that you suggested, slowly, and now the break points are nearly the same distance in the stroke. I think this is perfect.
I am extremely pleased.

One problem I noticed tho is that now the safety will not engage. It appears that the Comp hammer that I just installed has more material underneath the SA hook than the stock hammer does. This does not allow the safety to engage. Have you heard of this? I inspected the hammer and it appears that the manufacturer meant for there to be more material to reduce the SA pull/creep. It appears that I need to stone/grind/polish the left side of the ambi safety so that it works again.

Robert

[Stuart]

that is pretty common after installing the comp hammer..
I usually fit the pad on the safety to the sear..

[Aenimated1]

I made a small adjustment to the safety and now it works fine. DA is at 8 lbs and SA is at 44 oz. I must say that the competition hammer is awesome and well worth it. It reduces pull weight, creep, and reset. This pistols reset is tiny. I am too giddy to measure it right now but it is extremely short.

Thanks again to all the posters in this thread and the previous posters in the threads I referenced to complete this project. I will post a range report tomorrow.
Robert

[double pedro]

Like eerw said, it's pretty common to have to re-fit the safety when you change hammers.  Whether you modify the safety pad or the sear arm is a matter of preference - just make sure there is no play in the trigger after the safety is applied.  Otherwise, depending on the sear/hammer engagement geometry, you can run into a problem where pulling the trigger with the safety on doesn't drop the hammer, but the hammer then falls when the safety is released.  I've seen this on a very nice competition trigger job (my own) with relatively little engagement and a slight secondary angle on the sear - the safety has to be rock solid to work as it should.  I had to weld up the pad a little and do it again.

Sounds like you did a nice job on that CZ85.  Let us hear how it goes at the range.

[Aenimated1]

Double,
I decided to reduce the pad. I measured what I needed to remove and then did it with only four test fits. I did decide to ramp the safety slighly so that when it is engaged it is firm upon the sear arm. And it is very important to be safe with this pistol because of the small sear/hammer enagement and the lack of a FPSB. I will still certainly test the pistol before certifying it as a job well done.

I can already tell without firing the finished product that I will like it. It makes me want to get a CZ85 for myself. I have a few Sig Sauers in DA/SA and DAK but I just realized that this CZ is better, in my opinion. It is DA/SA but with a thumb safety. So you can carry it either condition 1 or condition 2 with no problems. Also when firing SA, if you have a light strike or a misfire, then you have second strike capability immediately at your disposal. Also it feels like the CZ grips are thinner than the Sigs yet have a higher capacity. All in all a great gun.

Robert

[Aenimated1]

Gentlemen,
For what it is worth, when you install a comp hammer make sure your sear is untouched and has the original positive angle intact. I reradiused the sear to match the old hammer. When I installed the new comp hammer upon testing it went full auto after a DA shot but normal operation for SA shots. I loaded five in the mag and it dispensed four shots with one DA trigger pull. Interestingly it left the fifth round chambered but unfired. Needless to say this is undesireable and dangerous. Luckily nothing was hurt but my pride.

I fixed the problem immediately. It seems that when bench testing the pistol everything was fine. Apparently when firing some movement of the gun or the operator created a situation where the radiused sear was jumping over the hammer notch when firing.

Please chime in if you have any helpful information.

Robert

[Stuart]

yes..if using the comp hammer..with the shallow hooks..leave the sharp edge on the sear..it is needed.
if you radius or cut a secondary angle..you will take the chance it will slip off the hooks and follow.

[double pedro]

Robert - Yikes!  Glad nothing was damaged and no one was hurt.  The hammer hooks on the competition hammer are very shallow.  I've seen them work fine with stock sears but the engagement is very small and at some point you may need to make the hooks deeper even with a stock sear.  Part of the problem is sear geometry as you mention, but also if the engagement is light and reset is short enough, I think a sort of "bump" firing situation may occur where the recoil resets the trigger and the slide going into battery may provide enough of a bump to fire the next shot.  This will depend somewhat on the shooter, grip, ammo, etc. 

You can sort of check this at the bench by holding the slide back with the trigger pulled and simultaneously dropping the slide and start to release the trigger.  If the hammer falls you likely have a problem.  If it doesn't, you still may have a problem. 

FWIW, I've had no problems with trigger resets in the 0.130" range and slight positive enagement of the sear and hammer.  I have run into the occasional double below 0.100" but this will also depend on the engagement geomtery, wear, etc.  I try to set up the engagement of the sear leg and trigger bar with no backlash upon reset (taking out the backlash gives the most sear/hammer engagement for a given amount of reset).  Then I deal with the hammer hooks - I may have to balance the sear geometry vs length of the engagement to get the reset to where I like it.  Finally, I make sure the sear still clears the half-cocked notch when the SA breaks.  If not, the notch must be lowered as well.

Oh, one more thing - the ejector cage that holds the sear can develop some play in its fit inside the frame.  When this happens, the play has to be "taken up" in the trigger pull adding to the length of the trigger pull and the reset.  At the same time, it doesn't add to the sear/hammer engagement and may reduce the dynamic integrity of the engagement by making it easier for the hammer to slip/bounce off of the sear during the recoil cycle (just a WAG on my part).  In any case, the fit of the ejector cage in the frame must be rock solid, IMO, anytime you start reducing the hammer/sear engagment from factory - if it starts to develop play you could run into problems at some point.