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pault418

KSC USP Gas gun vents all its gas

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I have a KSC USP (not ns2) and everytime I fill up a mag and pull the trigger, all the gas comes spewing out of the magazine. I tested this with two different magazines and same thing happened so it must be soemthing wrong with the gun. Here's a video that basically sums it up:

 

 

Note: skip to :48 seconds where he actually demonstrates the problem.

 

Any help would be appreciated!

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I have a KSC USP (not ns2) and everytime I fill up a mag and pull the trigger, all the gas comes spewing out of the magazine. I tested this with two different magazines and same thing happened so it must be soemthing wrong with the gun. Here's a video that basically sums it up:

 

 

Note: skip to :48 seconds where he actually demonstrates the problem.

 

Any help would be appreciated!

 

there are 3 symptoms of broken (cracked) loading nozzle body in KSC GBB

 

1. venting all of the gas

2. weak blowback (slide stuck and won't cycle fully)

3. low FPS

 

I cannot download the movie, but I suggest you to dissassemble the slide to see what happened

I am not sure, but I think older version KSC GBB had stainless steel nozzle ... dunno about the loading nozzle body

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there are 3 symptoms of broken (cracked) loading nozzle body in KSC GBB

 

1. venting all of the gas

2. weak blowback (slide stuck and won't cycle fully)

3. low FPS

 

I cannot download the movie, but I suggest you to dissassemble the slide to see what happened

I am not sure, but I think older version KSC GBB had stainless steel nozzle ... dunno about the loading nozzle body

 

 

 

Thanks for the tip, where is the loading nozzle on the gun, where should it be found? thanks

 

heres a diagram of the gun. Can you tell me what part might be the problem?

 

http://www.airsplat.com/Manuals/GP-KSC-USP-COMP-13.jpg

Edited by rubisco

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Thanks for the tip, where is the loading nozzle on the gun, where should it be found? thanks

 

heres a diagram of the gun. Can you tell me what part might be the problem?

 

http://www.airsplat.com/Manuals/GP-KSC-USP-COMP-13.jpg

 

I think it should be number 22

 

loading nozzle tip is easy to spot, rack the slide back, put the slide stop and you will see a nozzle protruding from the opening (in realsteel it was for spent casing)

 

in older version USP it will be stainless

but in order to see the body, you need to disassemble the slide ... and see whether part no 22 is still intact or cracked

 

cracks are hard to see, you need to fully disassemble the slide and check for any damages

Edited by truelotus

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I think it should be number 22

 

loading nozzle tip is easy to spot, rack the slide back, put the slide stop and you will see a nozzle protruding from the opening (in realsteel it was for spent casing)

 

in older version USP it will be stainless

but in order to see the body, you need to disassemble the slide ... and see whether part no 22 is still intact or cracked

 

cracks are hard to see, you need to fully disassemble the slide and check for any damages

 

 

Ok, so I took the slide apart, put aside the outer barrel. I see the stainless steel loading nozzle. Should I disassembly the blowback chamber and take it out of the slide? Where do I go from here? not sure what crack im looking for. Thanks

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Ok, so I took the slide apart, put aside the outer barrel. I see the stainless steel loading nozzle. Should I disassembly the blowback chamber and take it out of the slide? Where do I go from here? not sure what crack im looking for. Thanks

 

 

well ... you should, because that's the only way to check the loading nozzle body ... here's an example from my KSC p226, which previously suffered from the same problem as yours ...

 

note that in KSC, loading nozzle tip and body is made from single piece of ABS plastic ... and this is slightly different with USP

 

now ... this is KSC P226R loading muzzle

IMG_0684_resize.jpg

 

did you see the flaws ?

 

here it is again

 

IMG_0685_resize.jpg

 

see the crack ?? it's in the right side of the body ... barely visible and cannot be seen or checked unless you disassemble the whole thing

 

IMG_0686_resize.jpg

 

see the crack ? ... that's making my KSC P226R vent all the gases after couple of shots with weak blowback ... replace this thing and everything is back to normal

 

of course I also recommend you to clean the gun, and lubricating it as needed, especially in hammer mechanism ...

if your hammer mechanism somewhat broke or too tight due to lack of lubrication, it may stuck and keep pushing the strike valve in the magazine, also

 

I hope my opinion may shed some light to your problem

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Lotus, I took out the blowback chamber and was unable to find any cracked components like some of your pictures. Everything seemed fine.

 

It seems to me that the problem is the trigger assembly. With just the lower receiver and the slide absent (so I could get a clear top view of the trigger mechanism working on the magazine), I put in the magazine and observed how the piece that pushes the valve to release gas continues to stay depressed on the valve even after I release my finger from the trigger. I believe, and this is only an educated guess, that after the trigger pulls, the piece hitting the valve should retract back a little so the valve isnt staying fully depressed (and venting out all the gas as a consequence). However, I'm not really sure how to fix it even if that is the problem. Do I have to completely disassembly the frame?

 

Thanks for the help so far, much appreciated.

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Check out your Part #57 - lower right of diagram

 

http://store.kwausa.com/images/diagrams/gbb/kp45.jpg

 

See if there is any visible damage. When the slide blows back (does it even blow back?), it should press down on this part which releases the valve knocker. If you cannot see any damage, then pull the trigger, recock the hammer manually (the valve knocker should not "release" when doing this), and then push down on the piece in question and see if the valve knocker releases

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Check out your Part #57 - lower right of diagram

 

http://store.kwausa.com/images/diagrams/gbb/kp45.jpg

 

See if there is any visible damage. When the slide blows back (does it even blow back?), it should press down on this part which releases the valve knocker. If you cannot see any damage, then pull the trigger, recock the hammer manually (the valve knocker should not "release" when doing this), and then push down on the piece in question and see if the valve knocker releases

 

 

 

The slide "tries" to blowback but isn't able to fully. it basically blows back identical to the youtube video.

 

So I recocked the hammer manually and I see the valve knocker. As I push down on the valve knocker, I see the piece pushing the valve on the magazine move back. I can see where this WOULDNT allow all the air to vent out of the magazine. So how come it only works when I recock the hammer manually and have to push down on it for it to pull back on the valve? How would I go about fixing this?

 

There's seems to be no damage to the valve knocker, I found a quick tutorial on how to disassemble part 57 and it remains intact (no deformations or cracks)

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I'm starting to think it's not the trigger assembly. So I took two mags, filled both and tested it out. On the first mag, it vented the gas like usual. However, immediately, I disassembled the slide to see what position the valve knocker was in. Since the slide at least cycled partially ( more like 1/3) I guess the slide still activated the valve knocker and it wasn't making the trigger assembly completely depressing the magazine valve. I'm starting to think the problem is starting to lie in the upper slide. Maybe I should disassembly the complete slide to double check if there's anything wrong with the loading nozzle/whole blowback piston assembly. Thoughts?

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hmmm. It could be in the slide, are you by chance using an aftermarket slide made for a different system? I own a System 7 USP which vents all the gas when I use the slide meant for the old system. Everything fits on the slide like it should, but maybe they arent compatible

 

 

I believe the slide is fine. I have the old version KSC USP that came with a plastic slide and barrel. I got an aftermarket slide (prime) and metal barrel. When I installed it, the gun was shooting ok with the new metal slide.

 

It also might be worth mentioning that I used a propane adapter and loaded up magazines with propane. I believe you are suppose to put some silicon oil in the magazine along with the propane and fill it up (since green gas is essentially silicon mixed with propane). I can recall sometimes I didnt put any silicon in the gas feeding area and just loading straight up propane. Maybe I'm not using the propane adapter correctly. Think this may have caused any problems?

 

As for the timeline: From what I remember, the last time it successfully shot to the time it started venting gas, it was kept in storage for about 2-3 months. When I took it out of storage, that when I noticed the gas venting problems. However, when I took it out of storage, I did lube essential parts and the vent problem persists.

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The lube in the propane is mainly for the o-rings, I seriously doubt it would cause this issue. As for the storage, idk. Maybe its just some rust somewhere. The last thing I could offer is to see if there is anything out of place inside the blowback unit (a loose o-ring, bent valve, anything that doesnt look ordinary). I would take the blowback unit completely apart and see if all the pieces are still intact. I mean unless the slide is just being difficult, its possible that not enough gas is being sent to the rear to blow it back

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Found the solution guys. So, I looked at the loading muzzle (#22) again to see if it was cracked (it wasn't). However, the two tiny springs on the muzzle (called cylinder return spring part #25 http://store.kwausa.com/images/diagrams/gbb/kp45.jpg ) one was missing and the other one was warped. Either way, the loading muzzle did not return AT ALL due to the absence of these two springs. Not sure how they got that way in the first place.

 

I notice that when I try to put the loading muzzle (part #22) back on the blowback assembly (part # 132, 125, 126), it did not fit onto it smoothly. There was in fact a lot of resistence from part 132# and I had to use a bit of force to put #22 back on. I guess this is why the two springs eventually worn out/fell out because of the increased tension they experienced from the friction between #22 and #132? Either way, I should take some precautionary measures to make sure this doesn't happen again. Any other ideas how they may have become that way?

 

Special thanks true lotus for the pictures and heckler for guiding me in the right direction. Hope this thread will help anyone else who may have this problem of venting gas.

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Found the solution guys. So, I looked at the loading muzzle (#22) again to see if it was cracked (it wasn't). However, the two tiny springs on the muzzle (called cylinder return spring part #25 http://store.kwausa.com/images/diagrams/gbb/kp45.jpg ) one was missing and the other one was warped. Either way, the loading muzzle did not return AT ALL due to the absence of these two springs. Not sure how they got that way in the first place.

 

I notice that when I try to put the loading muzzle (part #22) back on the blowback assembly (part # 132, 125, 126), it did not fit onto it smoothly. There was in fact a lot of resistence from part 132# and I had to use a bit of force to put #22 back on. I guess this is why the two springs eventually worn out/fell out because of the increased tension they experienced from the friction between #22 and #132? Either way, I should take some precautionary measures to make sure this doesn't happen again. Any other ideas how they may have become that way?

 

Special thanks true lotus for the pictures and heckler for guiding me in the right direction. Hope this thread will help anyone else who may have this problem of venting gas.

 

 

you're welcome, rubisco ...

 

I try to pry my KSC USP compact last night (just got it 3 days ago) and found it to be system 7 :D

 

about the spring ... most of KSC older version GBB did have problem on that tiny spring ... my KSC glock 18C also suffers from the same problem ... though it only prevents the gun to shoot in full auto mode ... that's why I mislook about this spring, since my glock 18C still fires in semi auto quite well

 

don't forget to lube it all :D

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you're welcome, rubisco ...

 

I try to pry my KSC USP compact last night (just got it 3 days ago) and found it to be system 7 :D

 

about the spring ... most of KSC older version GBB did have problem on that tiny spring ... my KSC glock 18C also suffers from the same problem ... though it only prevents the gun to shoot in full auto mode ... that's why I mislook about this spring, since my glock 18C still fires in semi auto quite well

 

don't forget to lube it all :D

 

You are right. The two small springs (part 25) wasn't the main issue. It was part 23 on the blowback assembly. On the KSC, that rubber part somehow moved all the way up the length of that blowback assembly and wasn't in the right position. I overlooked this and forgot to update the post. But yeah, the very very main culprit was part 23 not being in the right position on the groove of the blowback area. I suppose this rubber- O causes some seal underneath part 22 (nozzle) and prevents the gas blowback from venting out all the gas. Now, I'm not sure how the rubber O part got moved in the first place....

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