TM PX4 piston head swollen

[Pepperisit]

My Marui PX4 was not returning to battery fully last game and the problem was getting worse.
I field stripped it and the loading nozzle was not moving freely. I assumed that the nozzle spring had gone.
Once home and taken the whole unit out of the slide the spring is there, intact and was in the correct placement.
I removed the rubber piece (Piston head?) from the unit and the loading nozzle moves back and forward unimpeded and the spring goes back to working as it should.
Hence I am assuming that the rubber piece has swollen up from the silicone spray (I did liberally coat it as first off I thought it was just dry).

I have washed it in hot soapy water and this doesn't seem to have affected it.
Can I but a replacement or does anyone have any better ideas?


The part I am referring to is PX-10 (as I'm sure my terminology isn't right!)



Thanks,
Chris

[Richard_severn]

Re: TM PX4 piston head swollen

If all you have used on it is silicone spray I would question what else is in the spray. as it shoulden't damaged the piston head.

You can obtain spares. Possibly look at a uprated one that's aluminium with a sealing oring and ports to force the oring out. They cost about 15 quid.
They also increase gas efficiency i have been told.
Just search 9 ball Dyna Piston head. I got mine from Zeroone but i have a 1911 and it wont be compatible with yours(from what it says on the packaging)
Link to the one for sale on Zeroone

[Danny_boy85]

Re: TM PX4 piston head swollen

Search for a PDI piston head for the PX4. The piston heads for 1911's and 226's wont fit as the PX4 is larger. But it will be the best £12 you will ever spend.

PDI Winter Piston Head.

Will solve all your issues

Oh and yes, change your silicone spray if its made that swell! Also maybe not apply so much also. Only needs it when its dry.

[Pepperisit]

Re: TM PX4 piston head swollen

Is 3 in one silicone spray... been using it for years and this is the first issue!
But yeh i'm sure that I put too much on haha.
Thanks /I'll have a look for that.

Are there reasons to replace the piston head anyway?

[Richard_severn]

Re: TM PX4 piston head swollen

What's the %of actual silicone in the spray as lots have a tiny percentage

You would replace the piston as it gives about a 10 fps boost and improves gas efficency as less gas escapes out of the blow back housing so the gum recoils quicker. That's my understanding anyway but I'm rather new to this

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[Pepperisit]

Re: TM PX4 piston head swollen

Well atm its working with a 100% airseal for the first shot! but its then too good after that and the unit won't return haha.

The spray doesn't say on the can I'll google later. Thanks again though

[Richard_severn]

Re: TM PX4 piston head swollen

You haven't lost the spring have you the one above the blowback unit? it must be pretty bad if the slide moving back to battery doesn't push it into position.
Mine is a little sticky but it has a new housing and piston head so probably needs a few rounds through it before it eases up

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[Pepperisit]

Re: TM PX4 piston head swollen

No the spring is there, and i also have spares now as i bought a replacement before I even took the unit apart haha

[Richard_severn]

Re: TM PX4 piston head swollen

Spares are always a good thing to have to hand hope you sort it out

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