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CZ P-09 random blowback version?

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Old September 10th, 2018, 22:58   #1
Mukaluk
 
Join Date: Feb 2007
CZ P-09 random blowback version?

I have three green gas mags and three CO2 mags. All six mags I get the same behaviour so I really don't think it's a mag problem. I get completely random levels of blowback and FPS. Everything from really snappy to a little sluggish to wet propane spewing out from under the slide and a bb rolling out the barrel to a complete jam up. When it does jam up its always on the way back and always in the position photographed. Everything I can get to with a field strip (no tools) has been cleaned inspected and lubricated properly. When I manually rack the slide everything feels smooth, there is a SLIGHT resistance in the action when I have an empty mag up against the nozzle and at the point when the nozzle gets pulled away from the inner barrel and back into the blowback housing. I have no problem maintaining my other GBB pistols and GBBR. Gun has performed this way since the beginning. I can go through a whole mag and it works flawlessly and then that same mag another time with same bbs and same full charge of propane will just spew gas and/or barely cycle. Cool down does seem to agravate thr issue like if i shoot burts and for sure if i mag dump. I've scoured multiple airsoft forums and reddit and have a found a few people with the exact same problem but no solves. The thing that stumps me is the complete randomness when no variables (bb type, mag pressure, temoerature, angle when firing etc) change the blowback is just totally unpredictable. I have lots of money in mags so it considering just getting the new version with the tall supressor sights and using this one for parts BUT I'm hesitant, due to this.

Any input is much appreciated.
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Old September 11th, 2018, 07:12   #2
Drakker
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Its probably a cracked nozzle. Inspect it thoroughly and bend it sligthly, it will probably reveal a crack or gap. If its not the nozzle, check the seal on your piston head and make sure the valve inside the nozzle moves smoothly and that there's nothing stuck in it, but I would put my money on the nozzle.
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Old September 16th, 2018, 00:57   #3
Mukaluk
 
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Disassembled blowback housing and nozzle: Nozzle is sound. Air seal between nozzle and piston head is perfect as far as I can tell. Rocket/floating valve functions fine manually. Took nozzle apart. O ring is good on the rocket valve and it seals properly when closed (blow tested compression on the rocket valve and piston head). There was a little rust and corrosion on part of the rocket valve spring I cleaned that and lightly oiled it as well as the o-ring. Cut two coils off the recoil spring as it is wicked stiff thought maybe gas pressure had trouble overcoming it. Now I reassembled and tested it still has random blowback strength performance hasn't appeared to change or maybe a very slight improvement as it hasn't actually jammed up again. Maybe I'll get into the hammer/valve knocker next.
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Old September 16th, 2018, 06:53   #4
Drakker
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Inspect the seal between the nozzle and the mags. Are the magazines sitting too low? It might be a magazine catch issue. They might also be sitting too high, but that's rarer. Try to push the magazine up with your hand while firing and see if its better or worse. Does the magazine have any play in the magwell?

Another possibility is that there is something impeding the movement of the valve knocker. Or one of the parts linking to the valve knocker is damaged.
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