Broke my Witness Long Slide ... again!

[Walt-Sherrill]

Was shooting my Long Slide during our IDPA practice session Friday night.  Started shooting hammer down.

Found that whenever I loaded a fresh magazine, chambered a round, and then lowered the hammer (for a hammer-down start), the gun would NOT fire when I pulled the trigger.  

Everything worked, but the hammer fall wasn't quite the same.

(I had been working on the trigger bar, but just didn't see how THAT could have anything to do with the problem.)

I left messages on the TFL's "The Smithy" forum, and on George Stringer's "The Gun Doctor" forum.

Suggestions were:

1) I may not have fitted the trigger bar right.  [Not likely; there's not much you can do wrong, if you do it at all...]

2) Maybe I took too much metal off the Trigger Bar making it fit. [Unlikely, as I did nothing to affect the LENGTH or PULL of the trigger bar, only its width and smoothness.]

3) Weak hammer spring.  [My first guess... but I couldn't explain why it was ONLY a problem from a DA start from a newly chambered round.]

4) Broken firing pin or damaged firing pin spring.  [Didn't seem likely, either].

5) Something buggered in the interrupter/trigger bar interface with the sear/hammer.  A possibility.

6) A bad lot of ammo.  Another REMOTE possibility.

In my mind, only 2,5 and 6 were  the only realistic possibilities, and I was shooting CCI Blazer ammo, which has been a solid performer for me in the past.

Well, I accidentally found the problem and fixed it easily.  Its something that COULD happen to CZs.

I'll post the answer later today or early tomorrow, but would like to see if others here can come up with the solution.  It surprised the crap out of me... (I would NEVER have consciously looked THERE for the solution.)

No fair cheating and looking at the answer I posted on TFL...
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[czechup]

Was it a bent main spring strut?  I had this problem with a Witness after a trigger job once.

[Walt-Sherrill]

No.  Not a bent mainspring strut... although I could see how it might demonstrate the same traits.  

(Good suggestion, though!  Another one I would NOT have thought of...)

By the way: the strut in a CZ is made much longer than a Witness, and might be even MORE easily damaged.

[czechup]

The strange  part of the bent main spring strut is that it happened while the sear assembly was out of the gun but the hammer had been installed and worked previously.  That made me think that it was something in the DA mechanism.  After some more DA polishing which didn't relieve the problem, I traced it back to the main spring strut and then had to figure which way to bend it to  straighten it.

[Walt-Sherrill]

It was a totally buggered firing pin block spring -- item 59 in the diagram above.  They seem to be very similar in the Witness and CZ.

Both ends of the spring were bent and deformed and it was apparently holding/jamming the firing pin block such that it wasn't functioning properly.

I pulled the firing pin to make sure it wasn't broken, and when the FPB dropped out, the problem seemed obvious.   (I was able to reshape the spring by sliding it onto the firing pin, which is the proper diameter.)   After reassembling, it returned to its normal reliability.

I'll order a new spring from EAA this week.  (Or from Brownells, if they still carry this part.)