CZ 75 pre B Trigger Problems

[Sportsman762]

This is my first post, however I have been a long time lurker.  This forum is full of knowledge and has answered many of my questions.  I have searched past threads and have been unable to find an answer to the problems that my CZ 75 pre B is having.  I apologize for the long post but I tried to fit as much detail in as possible.  Please let me know if something needs clarified.

My CZ 75 pre B trigger is dropping to half cock, or not dropping at all in double action or after the first shot. The gun is a CZ 75 pre B made in 1991 that I recently purchased.  This is an Interarms surplus import and has seen some heavy wear. The gun works as it should in single action for the first shot.
I discovered these problems with the gun shortly after purchasing it.  To try to rectify it I replaced all the springs in the gun, including the trigger bar lift spring, I also thoroughly cleaned the gun.  The problem did not change.  I have a very slow and steady trigger pull, this exasperates the problem.  I used snap caps with a magazine or an empty gun to diagnose the problem.  The problems did not change depending on snap caps or empty gun.  These problems also occur with live rounds.

Double Action
The trigger pull is relatively smooth in double action, and is far better than my 75B.  However the hammer will not always fall.  Pulling on the trigger harder does not cause it to fall. If you tap the hammer or shake the gun then the hammer will fall.  The hammer will fall sometimes, however there is a noticeable hesitation before it does so.  When it falls it is only at the rearmost travel of the trigger.  If I pull the trigger fast then DA works a large majority of the time.  The position of the gun does not appear to change the problems encountered.

Single Action after first shot.
The reset on the trigger is similar to the 75B, however the trigger pull is much different.  After the shot I release the trigger to the reset point then precede to pull back for the next shot.  When pulling back on the trigger the hammer cams back about 1/16? then falls 1/8? forward before being moved back about 3/16? (reaching a position slightly further back then when it first started moving back).  Then the hammer will fall and fire or stay back until the trigger is let up.  If the hammer fails to fall then when releasing the trigger it will do one of 2 things: Fall to fire after 1/8? of trigger travel, the hammer will then follow the trigger as its released to half cock.
When the hammer is ?stuck? back if the gun is shaken or the hammer tapped then it will fall to fire.  If the gun is held upside down then it work most time with less hesitation compared to held upright.

With slide removed in single action
The hammer will not fall when the trigger is pulled.  A slight downward nudge on the trigger bar will cause the hammer to fall to fire.  A heavy push upwards on the trigger bar will cause the hammer to drop.  It requires about 2-3 times more pressure upwards on the trigger bar to cause the hammer to fall to fire.
When pressure is applied up or down on the trigger bar during the entire trigger pull then the gun will function, is also applies if the slide is on.

I suspect the problems are related.

Does anyone have any suggestions on how to fix this?

[Tok36]

Welcome to the forums.

Sounds disconector related, though i am unclear as to how the SA issues with the slide off are related specifically. Let me do some digging this is one of the weird ones that dose not come up often, though i believe i have seen it before. I am also interested to hear other forum members input.

Very thoroughly described btw. It is appreciated.

Edit: First things first. You stated that you installed a replacement trigger bar spring. Let us make sure it is adjusted correctly so we can count it out of the equation.

This can be accomplished by following these steps. (Source: http://www.czfirearms.us/index.php?topic=66124.0)

1. Remove the slide
2. Cock the hammer in SA
3. Push the trigger bar down all the way, then pull the trigger all the way back, then release the trigger bar but keep the trigger pulled back.
4. The hammer should now be fully cocked in SA and you should be holding the trigger all the way back.
5. SLOWLY let the trigger go forward and watch the 2 humps in the trigger bar - one will jump up sooner than the other (Viewed from the rear)
6. The one that jumps up first has to much "up" tension on the trigger bar support spring (#34)
7. Bend the #34 down at little at a time until both sides of the trigger bar pop up at the same time.

[cntrydawwwg]

I'm gonna go with Toks trigger bar spring theory. Also make sure to restake the TB screw.
   

[ThompsonCustom]

The trigger bar spring sounds like its causing the SA issue what Tok said will work great for your gun. If the right side of the trigger bar comes up first it can give u a false reset.

Also sounds like you have a DA timing issue. Easiest way to test this would be to swap the disco out for a new one, i have a handful of disco's your more than welcome to have one just shoot me a pm with your address and ill send it to ya.

[Sportsman762]

Tok36 thanks for the welcome.  Your suggestion of properly adjusting the trigger bar spring got single action with the slide off working.

There is still a hesitation when the trigger is pulled before the hammer drops when on followup shots.  I am taking ThompsonCustom up on his generous offer of a disco.  Once I receive and install it I will report back with the results.

One problem down, one more to go.  I would have never figured out the spring problem without everyone's help.
Thank you!

[Tok36]

Nice, let us know how it goes.

You mentioned that the pistol had seen some heavy wear, it might be good idea to closely inspect the hammer hook/sear engagement. Make sure the sear is lifting up far enough to clear the hammer hooks completely during its travel. This can be accomplished by pulling the trigger back and rocking the hammer back and forth through its full travel. Look and listen for any contact between the underside of the sear and the top of the hammer hooks. If it is rubbing it may create issues down the line.

You can also visually inspect the lower edge/corner of the sear and the top edge/corner of the hammer hooks for rounding or excessive wear. The corners should be nice and sharp.

[M1A4ME]

I wouldn't let the hammer "fall" without the slide being in place. 

Without the back of the slide/firing pin to strike when the hammer falls from a trigger pull the hammer will smack the frame pretty hard with the lower part of the hammer.  Neither the hammer nor the frame are designed to make hard contact that way.

If you're going to pull the trigger with the slide off, be sure to use a thumb/finger on the opposite hand to keep the hammer from just striking with full force against the frame.

[Sportsman762]

I checked per ThompsonCustom's advice and the trigger bar spring is in the correct spot on the trigger bar.

[/quote]

You mentioned that the pistol had seen some heavy wear, it might be good idea to closely inspect the hammer hook/sear engagement. Make sure the sear is lifting up far enough to clear the hammer hooks completely during its travel. This can be accomplished by pulling the trigger back and rocking the hammer back and forth through its full travel. Look and listen for any contact between the underside of the sear and the top of the hammer hooks. If it is rubbing it may create issues down the line.

Using the process that Tok36 described in his post I checked the hammer hook / sear engagement. There is no sounds of contact nor does it feel like the hammer is making contact with the sear through all of the rearward travel.  However when when letting the hammer down slowly it I feel a slight resistance about 1/16" from the rear. It feels like the hammer is catching slightly on something, however it is very slight and not enough to hold up the hammer. I was looking at the great graphics on http://www.czfirearms.us/index.php?topic=73586.0 the Action Timing Thread and it appears to be in about the same place as the hammer would engage the sear after a shot has been fired.  After this slight catch there does not feel nor sound like there is any further contact.

[Tok36]

If i am reading you correctly it could be the disco contacting the trigger bar witch would be related to the timing issue that ThompsonCustom mentioned above. I guess i might also take a look at the hammer strut and hammer clearance to the slide notch.

[Sportsman762]

I fitted the new disco and it works great!  Thank you everyone for the advice.

[ThompsonCustom]

Good to hear it all worked out.