Glock 17 dumping gas

[[Avtomat]]

I have a little dilemma in my hands and i was wondering if you folks can shine some light on it.

The GBB is a Army Glock 17 has a full metal slide and is running on propane.

The gun is fairly new and after firing a total of about 8-9 mags it started to dump all the gas on the pull of the trigger, the slide would state stationary while the gas would escape though the barrel in a cloud of gas:?. I had mad a mistake by lubing only with the light weight oil supplied with the propane adapter for the first 9 mags.

after talking to CNDstalker i went out and brought some 10wt silicone shock oil. I stripped the gun, wiped off the old oil and appiled the new in needed areas like the frame rail, trigger mech and the hammer mech as told and working that in as well (possibility that hammer is malfunctioning). After doing that i fired a mag and it was great but i noticed the power in the kick was weaker in feel then before and near the end the mag had dumped the gas again.

Then a day after a leak starts up at the fill valve.

could all these problems be caused by a bad mag? or something else. The mag was treated well and was lubed. It is also fairly new as well.

problems in short
-sluggish blowback
-gas dump

any help is appreciated. :?

[MadMax]

Bleh. Pistol trigger internals should not be lubricated. Goopy trigger bits can accumulate abrasive sand and dust which generates a coating of what I call GBB smegma. Truth is, silicone oil altogether is a crummy lubricant. It has no retention properties and will spread to a molecular thin layer which offers no high pressure film protection to metal on metal contact. The only reason I offer it in the GunGas kit is because it is inert and good for conditioning rubber parts. The very low viscosity usually blasts out of the barrel instead of collecting into a smeary fouled coating.

Inadequate lubrication is almost never the cause of mechanical failure in GBBs. Usually something more explicit has gone wrong. Judging from your first symptom of gas venting with no slide movement, I would guess that an important valve in your nozzle body wasn't working right so it would not shut off breech flow and switch into blowback mode.

After a disassembly and cleaning you might have gotten it working right or it it got unseized just by moving things around. I still suspect the reed valve (if it exists) in your nozzle body. If it's not pushing forward and closing the breech flow it will not direct gas to the blowback efficiently.

I'm guessing that your GBB has most of the operating principles of all other GBBs.

As to your bad fill valve, try jiggling the stem around with your adaptor tip a bit. Sometimes valves seal up with a bit of manipulation. You can also try a drop of lube in your propane adaptor to wet the gas a bit on your next fill.

[m102404]

I built a Hicapa 5.1 last night out of spare parts and I was getting the same issue. First mag or two worked so-so...then either excessive gas vent with each shot or else big gas dump on the first shot.

Now, I've never used anything but AI 1.5wt silicone oil in the mags to keep them lubed...and I probably use way too little...and have probably neglected them more than once. But I shoot pretty regularly, so all in all they stay ok.

I've definitely been guilty of using too much silicone oil to lube the blowback unit and trigger/hammer assembly. But like MadMax said, silicone oil "dries" up and I just wipe any excess off.

In the pistol I built last night, the hammer assembly was pretty much bone dry. There was some grease crud that had dried up, a little graphite powder from when I tried that out once, but otherwise no real lubrication. Still works ok. I probably should lubricate the bearing surfaces...

The venting was due to a metal upgrade bulb and spring that I had laying around and I had put into the nozzle assembly to replace the stock one. On the HiCapa nozzle, there's a little clip that holds the bulb and spring into the nozzle (not sure on your model). At first I thought that I had screwed in the retaining screw too far and it was stopping/clipping the bulb inside. But that wasn't the case. It's supposed to make each shot harder/faster.

I ended up swapping back in the stock bulb/spring and the pistol shoots "normal".

Anyway, there's a bunch of things that can go wrong on a GBB and cause it to vent or misbehave. Mag to chamber fitment, broken/cracked nozzle, stuck bulb/reed, sticking main valve, etc.... Unless you're pretty sharp and feel comfortable interpreting parts diagrams, translating that into what does what and then taking your pistol apart...take it to someone who can do that for you. (not me...I barely understand what I'm doing...)

[[Avtomat]]

lol thanks guys.

Ill look at my manual and see where this reed valve is. I took the whole blowback mech out of the slide and slid the nozzle out. All i see is a nozzle and the part that slides around in the nozzle. What am i looking for as far as a malfunctioning reed valve?

I have a feeling it might be the gun it self and not the magazine .

[[Avtomat]]

I found a site on arnies that shows what the rocket valve is and how it looks like from the outside. Here

looks pretty useful. So in this case the reed on mine is.. snapped? bent?

The poster of that article also experience similar issues with his glock so i am thinking this possibly the root of the problem .

Now.. anyone got a clue how to take it out?

[MadMax]

It's kind of hard to say as not many of us have experience with your particular make of GBB. I basically had to make educated guesses based on the symptoms you listed and an assumption that your GBB works on similar principles to other GBBs.

If I recall, the KSC Glock has a pin pushed through the side of the nozzle body which retains the reed valve. If your GBB has the same try pushing it out. Look for anything which might be holding in your reed valve.

We're pretty much stuck at this point. Text diagnosis is a very limited way to troubleshoot a GBB. At the very least we need some good photos.

[[Avtomat]]

I just took a look at the manual and the part were the reed valve usually is, is showing up as a small cylinder looking object with the same fins as a read valve. Ill see if i can extract the reed valve and take some pictures while i'm at it.

thanks a lot Carl

[[Avtomat]]

So i disassembled the nozzle and this is what i see.

From outside:


Nozzle:


retainer, spring and reed:

http://s17.photobucket.com/albums/b6...t=100_4604.jpg

Reed:


How it looks like when held in place:




So, after that i reassembled and tried to fire it. And on first shot all the gas was purged.. again.

[jasgud]

What about the rocket valve. My 23F is doing the same thing, got the part in yesterday. Testing it next week.

[MadMax]

Wow that helps a lot. It looks like a copy of the TM Hicapa blowback design. I guess it's a copy of their Glock.

Out of curiosity, could you try reassembling the whole thing without the spring?

I'm guessing that the valve reed is not popping forward and closing the opening to the breech so the gun never goes into the recoil mode. Without that spring it should go into recoil mode without pushing out a pellet because the reed pops forward immediately instead of when the barrel pressure drops when the pellet leaves the barrel.

[[Avtomat]]

Alright sounds like a good diagnostics test. I'll give it a try tomorrow morning.
What can i possibly do if it IS the spring. It is stock and showed no problems for the first 9 mags.

[MadMax]

If the gun recoils with the spring removed then I'd guess that it was too stiff. Look for a replacement which exerts a lower rate. You might be able to modify the existing spring if you're crafty with a pair of pliers.

[[Avtomat]]

Hey Carl, guess what? you win the prize. I removed the spring and lo and behold, it works.
Are these springs sold regularly in airsoft parts stores?

[MadMax]

Cha chinggg! It's actually a bit of a rare thing to actually find the direct cause of an obscure problem via online diagnosis.

Unfortunately your spring is not a commonly sold item. They don't break and they don't get lost often so there is little aftermarket supply of them. If you're handy with model building you could wind your own spring from piano wire from the hobby store. Failing that look for alternatives at a place like Active Surplus. Also look for wierd coincidences. Maybe a mag spring has a similar diameter to your spring so you could trim a bit off of a mag spring to use as a reed valve spring.

More fuel for my burning distaste for clone shops that duplicate stuff without really appreciating the intent behind a design...

If you have a friend in the States who can bounce stuff for you, try mcmastercarr.com or smallparts.com (SP ships to Canada).

Both carry a lot of springs and bits and may have something close to what you need. You need a spring of similar diameter and helix angle (lead) and wire gauge. Your replacement will have to reduce any one of these: wire gauge, free length, lower lead in order to exert less force on your reed valve. Failing that, try modifying your existing spring.

[[Avtomat]]

So currently my reed valve spring has more tension then usual. Any idea why this would randomly occur.

If i were to cut a bit of the spring off, how much am i cutting off or is it more of a guessing game.