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Again and surprisingly: The Gun Is Still Running

 

Broken gas seal,

 

Donuts described it long time ago.

 

DSC01039.jpg

Well, maybe it's just mine, or KJW still hasn't improved on their pistons, air seal is still good though, even if it looks funny. But this is also important.

 

 

 

Piston Seal may be rugged but it will be works. Probably it is to wide or it is widen after using.

My seal was bit rugged because I forget to greas the piston and did it after 1,5kbbs. So I've to cuted it down after first greasing and it still works fine.

 

 

 

Edited by Amadem
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vertical grips cause the bbs to drop down faster defeating the purpose of a houpup. red dots make u go blind, for everyone u hit it takes away a min of vision so it makes u accurate out of fear. T

Yeah man, we pretty much get it. There's no need to post 20 times about how bad your KJW is. Now, can you please go ahead and delete your account?

News Update: We are back to working on our KJW BCGs. I think we should have a production level prototype finished within the next 10 days so keep your eyes peeled. For those who may have missed th

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Piston Seal may be rugged but it will be works. Probably it is to wide or it is widen after using. My seal was bit rugged because I forget to greas the piston and did it after 1,5kbbs. So I've to cuted it down after first greasing and it still works fine.

 

Seem to be a material issue with the seal then. What we are all seeing is the material the seal in constructed from is either too soft.

 

OR the seal application is not perfect. Instead of using a 'Lip' seal maybe all that is needed is an 'O-Ring' for this application??? As that is essentially what we have now that the seal has torn,,,

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You have to pull the charging handle back to chamber the first BB if it's a fresh mag. If it's a reload, you need to hit the bolt catch tab to make the bolt return, thus chambering the first BB.

 

Thanks for the info, I see what you mean and it make sense. But, I still can not figure out why the bolt does not stop on the last shot.

Edited by enjoi74
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Raven1, Kjw's m4 persecuter.

 

Thank You!

 

All of my testing has been completed except for the full auto testing. If I had to stop and were not to evaluate the gun and give an honest opinion and recommendation.

 

I would recommend this gun with no problems. This gun is perfect for anyone who is buying their first GBB rifle. This gun is perfect for the once a month weekend airsoft player. This gun is good for the airsoft player never plays and goes to one big game a year airsoft player.

 

Keep in mind this is a new gun and is a version 1 that is still being perfected. Tanio Koba did so many things right from the very beginning,,,

Edited by Raven1
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PLEASE NOTE:

 

KJW has however responded to a previous inquiry regarding the warranty issue of the gun as the gun serial # is KJ00217 and falls within the KJW recall notice regarding the KJW M4 Buffer, Buffer spring and magazine recall,,,

 

Raven 1, do you think the buffer spring needs to have higher tension. If that is the case I might put spacer in the end of the buffer tube to increase the spring tension.

For me I did not have any major issues with my buffer. It became loose after two magazines, but it was fine after I tighten it.

There was no leaks in the magazine, but I think the recall for the magazine was to replace a spring in the magazine. It is probably something about the bolt stop issue.

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PLEASE NOTE:

 

KJW has however responded to a previous inquiry regarding the warranty issue of the gun as the gun serial # is KJ00217 and falls within the KJW recall notice regarding the KJW M4 Buffer, Buffer spring and magazine recall,,,

 

 

Raven 1, do you think the buffer spring needs to have higher tension. If that is the case I might put spacer in the end of the buffer tube to increase the spring tension.

For me I did not have any major issues with my buffer. It became loose after two magazines, but it was fine after I tighten it.

There was no leaks in the magazine, but I think the recall for the magazine was to replace a spring in the magazine. It is probably something about the bolt stop issue.

 

enjoi74 - What serial # is your gun?

 

Correct, KJW has identified and corrected the bolt stop issue. One is the buffer spring is slightly weaker and the buffer is now metal making it slightly heavier. What this does is increase the dwell time of the buffer inside of the buffer tube. In other words the buffer stays fully inserted into the buffer tube for a longer period of time - allowing the bolt catch more time to engage. Before the spring pressure begins to react and push the buffer back out reseting the BCG back into the upper receiver. The longer dwell time allows for the bolt stop to work properly.

 

The easiest example of dwell time to explain in layman terms is this. Take a baseball - throw it straight up into the air - watch the ball travel up - the ball slowly comes to a stop - hangs in the air for a split second - slowly begins to move back down - then moves at normal speed. The amount of time the ball - stops - hangs for a split second - begins to move - Is The Dwell Time.

 

The same works for a bolt carrier group - the correct weight buffer - correct spring pressure - allows the the BCG to hang back for that split second - allow the bolt catch to pop up - carrier begins to travel back - catches on bolt catch. If The System Is Designed Properly - The Bolt Catch On The Carrier Is In The Proper Location To Meet Up With The Engaged Bolt Catch = Minimizing Force = Minimizing Wear On Both Components!

 

Those of us who have a serial # 300 or below will have the bolt stop issue as the guns come with Delrin (a high strength polymer) and a strong(er) spring. This causes a shorter dwell time and less time for the bolt catch to engage!

 

I Can Not say for certain what is being replaced on the magazine as of yet. I have a business owner associate who is from Taiwan, we will being placing a phone call later tonight to have my parts questions answered. If the person we speak to is an engineer then we will ask more technical questions regarding the gun. I will be leaving here shortly to go to Gear Box Airsoft to chrono the gun and see what the current power output is,,,

Edited by Raven1
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Raven 1 thanks for the detailed info on how this works. I learned a lot. My serial # is KJ154. I guess once this part is replaced to let the bolt to stop consistently, then rof will probably decease right.

Also, I am wondering. Does it make the gun last longer if a person does not set their bolt to be stopped on the last shot than the one who does? I know dry firing a AEG is bad, but is it bad on a gbb as well?

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Output with duster should be in the 350fps range perhaps slightly more. However, Im working on an FPS adjsutment system that we will have test fitted in raven1's gun before too long. Keep checking back to see how that test goes. Supposing it goes well and works as intended I may be willing to make a few for those interested. As well we are working on an new piston design which removes the piston cup and instead uses an o-ring.

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Raven 1 thanks for the detailed info on how this works. I learned a lot. My serial # is KJ154. I guess once this part is replaced to let the bolt to stop consistently, then rof will probably decease right.

Also, I am wondering. Does it make the gun last longer if a person does not set their bolt to be stopped on the last shot than the one who does? I know dry firing a AEG is bad, but is it bad on a gbb as well?

 

Correct, the rate of fire will decrease slightly in full auto, you can't pull the trigger fast enough in semi auto to note a difference. However due to the light weight of the BCG assembly the rate of fire in full auto fire is not going to put you at a disadvantage on the field.

 

The answer is yes, dry firing on a GBB is not good for the over all health of the gun. Setting the bolt stop is personal preference, will it make the gun last longer? Sure, as long as you know the last shot is out and you stop. Just don't end up firing the gun 4 to 5 time before you realize it is empty. As then you are putting more wear on the gun than if you were running the bolt stop. Being that the gun in question is the Tanio Koba design M4, you are safe running the bolt stop after the last shot as a default.

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OR the seal application is not perfect. Instead of using a 'Lip' seal maybe all that is needed is an 'O-Ring' for this application??? As that is essentially what we have now that the seal has torn,,,

 

Thing is, its a cup for a reason.

 

Its there to form a seal in only one direction, that is, in direction towards the cup.

 

This is for when the gas to expands, it puts pressure against the cup causing it to expand to form a tight seal. This aids efficiency on sending the bolt carrier group into the buffer tube shot after shot.

 

Probably one of the reasons why this gun is so efficient on gas, since not alot is 'lost' from leaks in the system, where gas can escape.

 

 

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Thursday, September 3rd, 2009

 

1600 Hours

Temperature 110F / 43.33C Afternoon in Arizona

 

Propane Gas - .25g BBs

 

Propane Gas Used - Coleman Propane Fuel - http://www.thegreathardwarestore.com/Produ...&click=2744

 

- Firing Mode = Semi Auto - Slow Fire -

 

Test Fired 1 Magazine Through Gun And Chrono'd:

1st Shot = 480 fps - 146.3 mps

Last Shot = 441 fps - 134.4 mps

 

Surpisingly the gun still is shooting very hard although not any where near as consistent fps than as with nozzle plunger intact.

 

Keep in mind that 1/3 of the lip on the lips seal Is Not present. Nice,,,

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Thing is, its a cup for a reason.

 

Its there to form a seal in only one direction, that is, in direction towards the cup.

 

This is for when the gas to expands, it puts pressure against the cup causing it to expand to form a tight seal. This aids efficiency on sending the bolt carrier group into the buffer tube shot after shot.

 

Probably one of the reasons why this gun is so efficient on gas, since not alot is 'lost' from leaks in the system, where gas can escape.

 

If you think about it though, the cup would be deformed outward during the blowback cycle to create a good seal as well as during the return stroke of the bolt, except air is causing the deformation during the latter phase. The back of the bolt is open to normal atmostpheric pressure during blowback so no pressure is built up behind the cup. And during the part of the cycle where the bolt returns to the carrier pressure can be vented to atmosphere through the gas inlet on the bottom of the bolt. An o-ring can theoretically be used here because of those facts. This has been done as well in many aftermarket gbb pistol kits that use exactly the same design as the KJW m4 gbb.

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Actually I don't think you guys get what Raven1 is telling you. The gun had some internal parts FAIL and it still operates. In fact he ran another range test on it in its current state without any real issues. Gas efficiency has dropped, and mags cool down more due to the wasted gas, but he was able to get a whole mag off and have it lock back.

 

In addition he was running propane/green pressure gas at 100+degrees. That's pressure that will cook almost any gas gun.

 

I have a WA, and man, if something is just a little off, it WILL NOT function. In fact I have had this gun for a YEAR, and havent had it in a playable state yet.

 

Not Once.

 

It started life as an inokatsu, since bying that 1000$ gun, I have probably spent about 1500 minimum trying to get it to where i want i to be.

 

The KJW is amazing, just astoundingly good considering its cheaper then a WE. I mean its mags are like 35$?

 

I'm not saying its perfect, but I think that if someone wants to get into GBB rifles, the KJW is the current way to go, though the VFC might com and sink it.

 

 

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Can anybody tell me if a CA styled KAC RIS can fit on this gun and how well it does (wobble wise). If not cn it accept CA styled outer barrels on it?

 

Thanks in advance.

 

Yes, Classic Army RIS will fit provided you have the proper barrel nut for it to clear under / in the rail. The Classic Army AEG barrel will fit but needs 2 more additional cuts for the bolt BB extractor to clear and inner barrel to properly seat inside the outer barrel.

 

Please refer to post # 148 on page 8 where I detailed how the cuts were made.

 

The current barrel on the gun is a 10.5" Classic Army CQBR AEG Outer Barrel. The barrel has been modified with the 2 cuts on the barrel and it took about 30 minutes.

 

PM " t_hum " and he will be able to provide Exact Measurements on how, where the cuts need to be made.

 

Please refer to post # 186 on page 10 to see all that is installed on the gun.

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KJW Update

 

Friday, September 4th, 2009

 

0015 Hours

 

Made a phone call to KJW in Taiwan, a business associate of mine who is from Taiwan. And being a native of Taiwan who is obviously fluent in Taiwanese spoke with 'Clare' on the phone.

 

Cleared up what items needed to be ordered / what items are warranty / standing by for response email with quote and Paypal address to get my parts shipped state side.

 

Gotta love America - even in 'Red Neck' Arizona you can find a native person from the country you need goods and services from!

 

 

 

"It's A Small World After All, It's A Small World After All,It's A Small World After All, It's A Small, Small, World,,,,

 

 

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If you think about it though, the cup would be deformed outward during the blowback cycle to create a good seal as well as during the return stroke of the bolt, except air is causing the deformation during the latter phase. The back of the bolt is open to normal atmostpheric pressure during blowback so no pressure is built up behind the cup. And during the part of the cycle where the bolt returns to the carrier pressure can be vented to atmosphere through the gas inlet on the bottom of the bolt. An o-ring can theoretically be used here because of those facts. This has been done as well in many aftermarket gbb pistol kits that use exactly the same design as the KJW m4 gbb.

 

Good point, would be easier to replace an o ring too since they are generally more readily avaliable. I wonder if a pistol (1911 or similar) piston lid kit would fit on the KJW bolt, may have to get one to test.

 

Top effort Raven1, sounds like the KJW is the GBB of choice, will order one soon and post up reports as you have done soon!

 

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Good point, would be easier to replace an o ring too since they are generally more readily avaliable. I wonder if a pistol (1911 or similar) piston lid kit would fit on the KJW bolt, may have to get one to test.

 

Top effort Raven1, sounds like the KJW is the GBB of choice, will order one soon and post up reports as you have done soon!

 

The piston cup is a fair amount larger on the KJW unfortunately than any piston cup Ive ever seen for gbb pistols. Ill post pics of my prototype o ring piston this weekend for any interested parties.

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Prototype O-ring piston complete. Still have to test it but it seals very well currently.

 

photo.jpg

 

Sorry for the poor image quality. Better pics coming soon.

 

Wow, so it replaces the whole piston. Is that aluminum or steel? That looks nice, how much you plan to sell them for?

Also, are you plan to put some holes on top of the piston head to make a better seal.

Edited by enjoi74
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