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Every now and then we hear of a new Czechophile / CZ-52 fan who experiences the dreaded "trigger slap phenomenon" (TSP) where when a round is fired, the trigger violently - and sometimes painfully - snaps forward against the shooter's trigger finger.

At least, it can be distracting, and certainly does not contribute to accurate shooting.

After considerable banter and hypothesis, we finally "cured" the TSP problem.

It was a collaborative effort among several GB Members, and I was proud to have been a member of that team.

Here is the post, dug from the archives, where we finally got on to the real problem; if I can find subsequent postings in my archives I will post them as follow - ups as well.

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"Why ccg; aren't you a splendidly clever fellow; that is a jolly good idea!

Banker B, you seem to know a thing or two about gun-tweaking; if the plunger turns out to be the culprit, you might try taking a narrow stone to those "burrs", and see if that makes any difference. Check the notch in the top of the firing pin where it engages as well for any corresponding roughness or burring.

But whichever you choose to do, I hope that at your earliest opportunity you will go forth, shoot, and get back to us as to any changes in the trigger behavior, if any.

According to my calculations, there are essentially two places where this "trigger-slap" can be originating.
Now ccg, as clever as you are, you might be able to locate another one I have yet to consider, and you're a daisy if ye do!

The first one I thought of was the "Disconnect" lug that extends from the top of the trigger actuator bar on the right side, under the sideplate that runs from the trigger back to hook under the hammer pivot (the thing that has a little nut on the end that you can see if you take the right grip panel off). The Disconnect lug or "hand" sticks up between the grip panel and the lower edge of the slide, and if you have the slide off and pull the trigger with the safety off, you can see it waggle up and down. The top edge of it is tilted a little.

Look at the bottom of your slide, and you will see the corresponding quarter-circle cutout near it's right edge (which will be on the left if you're holding the slide upside-down). This is to allow the hand to extend up into the cutout when the slide is in battery, allowing the actuator to bear on the sear and drop the hammer. If the slide is out of battery, the hand is blocked by the slide rail (where it's not cut-out) and the actuator is pushed down and out of articulation with the sear - so pulling the trigger will not disengage the sear, drop the hammer, or fire the pistol.

At least that's how it's supposed to work; it seems, however, that if the slide is just a little bit - say about 1/8 of an inch from being completely closed - it is apt to fire anyway.
This means that an out-of-spec cartridge or short headspace on your CZ-52 might cause it to fire a wee bit out-of-battery, which is not all that good a thing, you know.

Now there are two actions of the slide in cycling operation, as I see it, which can translate to an impact or impulse of energy back to the trigger.

If you find any more, ccg (or anyone else out there), please advise us, so that we may include them into the existing paradigm.

Since it is reported that installation of a Firing Pin upgrade has cured this issue at least once so far, I have moved away from the actuator disconnect as the prime suspect and focused instead on the firing pin lock-out plunger.

At rest, the plunger is moved to it's lower position by the spring. In this position, it's "hook" engages the corresponding notch or cut-out on the top rear of the FP, locking it from moving forward or striking the primer. The bottom of the plunger should be flush with the central rail set, consisting of a raised rib running down the center of the breech end of the inside of the slide, which has a narrow notch milled along it's center.
When the slide is in place, the bottom end which is cut away on one side, leaving a semi-circular bearing surface, should rest upon the end of the lifter arm extension of the sear.

Again with the safety off and slide removed, you can see this little arm directly in front of the hammer move up when the trigger is pulled, and drop back down when it is released.

.............


When the arm is lifted, you may notice that it's articulating surface is tilted towards the breech end of the frame.

When the slide is in place, and the trigger is activated, the lifter engages the firing pin lockout plunger in the slide and lifts it. The locking "hook" lifts clear of the firing pin notch, allowing the pin to fly forward and strike the primer of the cartrige when struck by the falling hammer. As the hammer rebounds, the angled face of the "hook" is supposed to cam the firing pin back into it's rearward position, and as the action unlocks and the slide begins to move to the rear, the plunger backs off of the lifter hand and is pushed back down by it's spring, re-locking the firing pin until the trigger is pulled for the next shot.

At least that's how it's supposed to work, as near as I can tell.

Now if for some reason the plunger is coming back down a little too far, or the sear is rotating a little furthur than it should, that little arm is still going to be sticking up when the slide comes back for more and the bottom of the plunger is apt to fetch it a healthy whack, smacking it right back down smartly - and the stronger your recoil spring, in all likelyhood, the harder the whack.

If you trace the path of where that energy impulse is likely to be transmitted, guess what?; it ends up right at the trigger, smacking it forward against your finger about a nannosecond after your shot broke.

Make sense to you?

Now if you look at where the plunger goes in a slide that's been outfitted with a Harrington system, you might notice that the lockout plunger is rather conspicuous by it's absence.
There is, instead, a little hole through the pin shaft itself through which you poke a little pin to disengage a much shorter little retaining lug that is provided with the system in order to remove the FP.

The job of holding the pin back from bumbs, jars, and the inertia from when the slide slams home into battery is taken over by a stout little rebounder spring coiled around the Harrington Pin's nose. So the long and the short of it is, that there is nothing at all to strike the sear's lifter-arm as the slide runs home, thus no slap-down, and no corresponding trigger-slap.

This is not to say that some CZ-52s might not be having an issue with their trigger actuator disconnector hand getting fouled up somehow in it's little raceway in the slide; If that little hand gets smacked backwards as the slide comes back in recoil, it is going to snatch the bar backwards right along with it.... and the forward end of said bar is attached by a little pin to the top of the trigger, above the trigger's pivot-pin. Now a backwards snatch on top of the trigger is going to be translated into what kind of a whack underneath said fulcrum point? And how is your trigger-finger apt to percieve that sort of an energy impulse?

I rest my case, and stand ready for cross - examination.

Oh; BTW; I would, while I had the slide off, check that little "hand" as well as the groove along that side of the slide that it runs in for bright wear spots, burrs, nicks, or other signs of unusual bearing or collision.

Now if any of you with a trigger - slapping Czech-O-Matic are able to cure your weapon of this bad habit by application of any of the above speculation, I would appreciate knowing about it - and it just might make my day as well as yours!"


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Note: Some of the TSP "victims" later noticed that the sear extension on their COMs were not angled back properly, as is the one shown in my illustration, but flat or angled backwards.

When they stoned the angle to it's correct degree or replaced their sear, the TSP went away. Thus the elusive TSP mystery was solved and the problem cured, thanks to the GB Czech-O-Matic Research Team! {;^{)~

UJ
 
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