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PX4 decocker problems


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Is this the original WE PX4 or TM?

Anyways. I had a WE PX4 briefly and from what I recall when you push the de-cocker lever down it in turn presses down on the "trigger bar" mechanism and lowers the hammer. So I would guess that your de-cocking lever on the left-hand side has become deformed/worn from use and is no longer pushing down hard/far enough to de-cock the hammer.

Same on the right side but just not all the way broken yet.

EDIT: Or they are of course linked for ambidextrous operation and might have developed slop/play between the sides which makes one work better than the other.

Take the slide off, check the nubs going down into the slide under/in line with the de-cocking levers and see if they are worn/damaged. Check corresponding area in the frame and see how that looks.

It's been a while since I had one but I hope I recall correctly and that is also how the M9 models with de-cocker work.

As for fixing it, restoring worn material will be difficult or impossible so unless you can bend something back in shape, replacing the worn parts is the only solution.

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I've observed that it works normally if I press down on the slide. Otherwise, the space between the slide and the frame gets bigger and the half moon of the decocker lever is able to push the hammer's connector. It doesn't seem any part is worn, there's just more play between the frame and the slide.

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I got my TM in 2010, and the original decocker sear/lever was made out of a very soft metal that dented and stopped working after 40 or so activations.  The gap between the slide/frame and wear on the safety itself also contributes to this problem.  Detonator made an overpriced steel safety back in the day, but a WE safety works as well.  The WE lever (part #25 on KYAirsoft) is much better than the Marui version, but it is slightly too short to activate on a worn plastic slide.  I used a cheap soldering iron to attach a cut-up piece of copper from an old aeg selector plate.  This solution takes way too much effort, but it has held up very well.


The trigger spring, trigger bar spring, and slide catch are also things to look out for.


The soldering solution also fixed my slide lock problem on the TM USP compact, but it's honestly very tedious.



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14 hours ago, Wingmann said:

Yeah, part #25 is the decocking sear/lever.  If yours doesn't show any damage, it might be the safety.  It has been almost a decade, but I remember that my original parts had visible wear on them.  I bought the overpriced Detonator steel safety years ago because the Marui version got worn down quickly.


The spring (part #21) for the trigger bar broke on mine after a thousand or so trigger pulls, and the trigger spring (part #39) broke after a few hundred.  The faulty slide stops were probably only in the early batches; you're good if it doesn't break very early on.  Other than that, the gun is decent overall!

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