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mrtrump

CYMA dragunov upgrade problems

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I recently finished some upgrades on my CYMA cm057 dragunov. I cleaned the barrel with a cotton square and rubbing alcohol, installed a maple leaf macaron 70 degree packing and concomitant concave nub. Here are links to the items: 

https://www.airsoftatlanta.com/products/maple-leaf-aeg-rubber-70-degree (packing)                                

https://www.airsoftatlanta.com/products/maple-leaf-aeg-hop-up-tensioner-omega (nub) 

I also stretched the o ring around the piston head. I am overall pleased with the final result, but I have one fairly large problem: when I fired the gun, it only fired every other shot, made a very strange noise, and on the second trigger pull when it did fire, two bbs were fired. To isolate the problem, I first stripped away everything from the gun but the gearbox, to see if the problem was in the gearbox. The gearbox operated perfectly. No strange noise, a nice, crisp response, and it was a slightly quieter noise, less of a whine, because I shimmed the gears. I then held the inner barrel in place against the gearbox. No problems. I then reassembled the thing. Strange noise, only fired every other shot. I then did it all over again, and completely reassembled the gun. However, this time I accidentally lost the nub in my hop up unit and didnt realize it until later. This time, all went perfectly. When I realized that I didn't have the nub in, I went back and reinstalled it. At this point, I was suspicious that the factor causing the gun's malfunction was the presence of the hop up nub. So when I reinstalled the nub, I turned the hop up to the lowest setting. Everything worked. I turned the hop up slightly more. Worked fine. When I got to a certain point, and that point was not even very much hop up, the gun did the same thing I previously described. My question is why. How. Is it the hop up nub? It seems like it, but I could be wrong. Does it sound like anything else? Why does the hop up system cause malfunction, if that is indeed the cause? Thanks in advance. Also, at the low level of hop I had the hop up unit at when the gun did fire, fps was DRAMATICALLY reduced. 

Edited by mrtrump

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Yes...there are insights.
First off you have a CYMA.  Tolerances can be "loose".
What you are describing is a mis-alignment of your nozzle to hop-up chamber.  This also explains the drop in FPS.

When your hop is off.   There is no restrictions, so it can pop a bb in and fire.
However, the ML packing has a rather large contact patch.  With your nozzle mounted too high and the patch too far down in dial-in...you create an obstruction that is causing it to double feed.
 

The initial stroke is not strong enough to get the bb fully seated.  It takes a second bb to make up the gap to allow the nozzle to over come the contact patch and seat both bbs...thus I surmise is why you get the double shot.
 

Edited by Guges Mk3

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Well then, let's turn up the collaborative effort.  We can only collaborate to a certain amount via descriptions, which is what I done have based on your descriptions.

Post some pictures....for they are a 1000 words in worth.

Thing to look for is travel misalignment, fitment misalignment after "engagement" (nozzle in hop-up), tappet travel...is the front too thick and is preventing the nozzle from engaging correctly.

Helping us with pictures (good pictures) will allow us to help you.

 

Take a picture of each segment would be beneficial.

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Convert the image to another format, compress it down or upload it and share the image via a link to the image.  Or set up a remote pointer to the image.

 

Like this:  

9124ecb5389ffe600cb4dfb38c1c0b5d_1024x10

 

Which is inserted via an image link via a URL.
>>>>https://cdn.shopify.com/s/files/1/1085/9090/products/9124ecb5389ffe600cb4dfb38c1c0b5d_1024x1024.jpg<<<

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Here's a picture I took. The visible image is a side view to look for any misalignment. Sorry if it's a bad picture.

Here's a link to an image showing you the tappet plate on this gun. What you see is a tappet plate at almost full retraction:

file:///C:/Users/sirsk/Downloads/picture from the side.pdf

Here's a picture from a front view:

file:///C:/Users/sirsk/Downloads/picture from front.pdf

 

Hope this helps. If not, I can do everything over again.

Nozzle image.jpg

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Ummm...no...your links reference your C Drive on your computer.

You need to post them to a file share on the internet or upload them to the forum server.  Unless you open your personal computer as a webserver, which I don't recommend.

The one that did post is showing a nozzle on the cylinder tube as being dead on.  So, the other questions is what does it look like when the hop-up unit is inline and secured down.

 

Edited by Guges Mk3

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Here's a front view. Hope you like slack. I don't know how to upload an image to the forum server. 

https://files.slack.com/files-pri/T012QUU33EH-F012SANRMFU/picture_from_front.jpg (front)

 

The purpose of this image is so you can see the distance away from the front of the gearbox the tappet plate is at almost full retraction. I couldn't get the tappet plate to come forward without opening the gearbox for obvious reasons.

https://slack-files.com/T012QUU33EH-F013G71DEU8-ae425b86bf (side)

I'm not quite certain how I could look at the nozzle when the hop up unit is inline and secured down, because you can't see the nozzle when the hop up unit is over it. I could remove the packing, which would allow me to see better, but I'm not sure how that would be helpful, since I believe we're trying to figure out how the nozzle engages the lips of the packing. I hope this is helpful. Thanks in advance.

 

 

 

Edited by mrtrump

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Can you make them public images?  I have way to many accounts out on the net and it would benefit potentially other people helping you just by looking at a public image instead of having an account to see it.

As for inserting images...there is a drop down on the lower right...that is where you can add a link to an image or up load one into your post, like this.1177377904_ECapture.thumb.JPG.eb9d9e619143f45fc1cbe18c095d2655.JPG

Edited by Guges Mk3

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Public link showing a front view of the gearbox:

https://drive.google.com/open?id=1lCgMApqtHrmAoDF_SSptP1nE6vXEd4oK (front)

Here is a public link showing a side view. The purpose of this one is just to show you the distance from the front of the gearbox to the tappet plate at almost full retraction:
https://drive.google.com/open?id=1c_o1nOniINaPBw8M-xTFkXioLzDd7qnX (side)
 

And just for fun, here's one from inside the gearbox. The purpose is to show you how the nozzle sits on the tappet plate and how the tappet plate sits in the gearbox. I removed the tappet spring because it caused the tappet plate to stick out of the gearbox without the other half of the gearbox shell holding it in place, and I didn't want to hold it in place with my fingers for fear of obstructing the photo:
https://drive.google.com/open?id=1GpOqwvigAsNTe3d6j9I_CCR1Mmj7q5xT (gearbox view)

 

I hope that these help. Thanks in advance. Sorry for the technological incompetence, I swear I am younger than 25.

 

 

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Here you are. I hope at least one of these are helpful; 

1. https://drive.google.com/open?id=10QOM5PjkZfovpY8-Ugb1n1ZpQN1lFppy

2. https://drive.google.com/open?id=1_LOwRZx8XmxU-GOc7tDHF5pTCbxUvb6c

3. https://drive.google.com/open?id=1FlqvZNZXghe2orE19OHtco3W4TkATpmz

4. https://drive.google.com/open?id=19BU-0FF9tKMf3zVwuK0Ps9ldA-eRLR8A

5. https://drive.google.com/open?id=1PpynDri07W2q8p284jPNX7Ub9XtYxQxM

6. https://drive.google.com/open?id=1L-qr9PNDMs5bLRDToZ93ldw1QYaESL_W

7. https://drive.google.com/open?id=1_1ZmL3z6th8REHXB1qCiA3XJx54rgMqa

 

I apologize for the first inner barrel image I posted. When you said "now you need to throw some light down that barrel with the hop-up fully off" I interpreted "off" as "removed." I was confused about how that would help anything. Thanks in advance.

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Yes the packing is on the barrel in all the pictures. If you look in the third link from the bottom, you'll see a blue ring. That's the 70 degree maple leaf macaron packing. If you look in the bottom link, you'll also see maybe a small patch that protrudes slightly. That's the contact patch on the bucking.  When you say my barrel looks off kilter and left by a hair, what do you mean. Also, what do you suggest I do to remedy the issue with the packing and nub?

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Here you are;

https://drive.google.com/open?id=1mck7yVa_T8wQ4kjeDVTGxJKmXLj82fDg

 

https://drive.google.com/open?id=1bdNw6PhbQ7yOPpzGtt8OQn3T3PtAIIdy

 

You said that you say no problems with the packing or nub at this time. I thought nozzle misalignment was considered the most likely problem, not any component of the hop up system. Am I wrong? Thanks in advance. If these images are any help, what is the best route I can take to remedy the problem I am having?

 

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You have to take it "all" in context.  

You described an issue we can't see and you really can't fix just by snapping parts in and out.

You need to look at how it all ties together.  And now as this case develops...your really bad barrel maybe cause the packing to not seat correct and thus when you dial it up if starts up and sounds like it trying to jam a bb past an obstruction thus your mechbox noise.

 

Your barrel window is terrible (is this an "old CYMA"?)  If needs to be even.DSC06605.JPG

See the channel on either side of the delta contact patch.

That will NOT seat cleaning on your badly cut window.

You will need a small flat file to clean up that bad mill job to look like the window on the stainless barrel above.

Do you see why this maybe affecting your feed/sound issues?


 

NLBBCYMA.JPG

CYMABB.JPG

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I apologize for the poor response time.

I truly do not see a difference between the barrel of the stainless steel and my barrel, other than the obvious color. Remember my lack of experience. What difference am I looking at? Thanks in advance.

Also, on a side note, I know that this is not the correct discussion, but I removed some shims from the gearbox on my 1928 thompson as you said may fix the problem and it did work. It also saved some money. So thank you.

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I see. I will file the barrel asap. One question;

1. What about the tappet plate, nozzle misalignment, etc.? We simply moved on to the issue of the barrel without addressing the first issue. Do I need to pay any more attention to the nozzle-related issues? Thanks in advance.

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This is a picture of my maple leaf macaron packing. It is different from the picture of the one you posted, in which you said that the problem lies in the way the packing sits on the barrel window. Does that change anything?

https://drive.google.com/open?id=1tf-vrABrBmnHSdk1A6DFVgo6dJ-3NY3L

There is no 'channel' on either side of the contact patch. Nothing 'sits' on the barrel window in the same way that the delta packing you posted does. It all fits inside the barrel window. This seems significant to me, though it may not be. Should I still fix the mill job by filing anyway? Thanks in advance.

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I truly don't know if this is better. It could very possible be worse. Maybe because I do not have an eye for subtlety, but I do not see significant difference between my barrel and the stainless steel one. Thus, I did not entirely know when to stop filing. But here's what I've done. If I've made it worse, please do not hesitate to be blunt. 

https://drive.google.com/open?id=1zpKt5y9qDqfpYd4xxnCxcxgPWTsYVu6z

Also, if I did improve the mill job, is this likely to play any role in fixing the original problem for which this thread was created? Perhaps this is just my ignorance talking, but I truly do not see how the simple act of altering something so subtle could fix such a blatant problem. I'm truly not even sure I see a connection between the uneveness of the barrel window and the contact mound problem, as nothing actually contacts the part of the inner barrel window I was advised to file. Is it possible I may need to simply purchase a new inner barrel? Or that, againt everything I read on AirsoftAtlanta's product page about the packing I purchased, and the forums I read, that I purchased a packing and nub that are somehow incompatible with my aeg? Thanks in advance.

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AEG Packings work for AEG's - Period.

However, with a bad barrel window, the packing can't deploy cleanly into the barrel...that is most likely why with little dial up it works and with a lot of dial up it jams.  Imagine the nub pushing with slight dial in...it moves down a bit...but if the barrel window is too small AND wonky...its not going to deploy correctly and you dial it up more it just jams an "intrusion" into the barrel.  Thus blocking your shots.

You need a fine jeweler/fine flat file to clean this up now.  Even it out so the line is clean like the stainless barrel.  

Your barrel is no where as straight and clean as the stainless barrel.

Barrel File.JPG

Edited by Guges Mk3

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No...because if you buy a low grade barrel you will have the same issue.

And many "high grade" barrels are cut for Traditional Hop-Up packings.  This is why I always tell people that AEG upgrades are not snap in...you often need to mod it to allow it to work correctly.  Anyone spouting just buy it and drop it in are "ignorant" on how things work in Airsoft.  However if you bought a ML barrel...it would be a drop in upgrade.

Plus not many barrels are "cut" for a ML packings.  60% of the barrels out there have to be modified to allow the ML packing to work to it's full potential.

One very respected Tech from Norway with over 9 years of experience just learned that Prommy (very high grade Japanese barrel) has a window that is too small for ML to work properly.  He took a massive amount of material out and got it to work right and now he is ranging out to 70M, out shooting most "Sniper/BAR" rifles out of the box at just only 400fps.

Edited by Guges Mk3

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23 hours ago, Guges Mk3 said:

You need a fine jeweler/fine flat file to clean this up now.  Even it out so the line is clean like the stainless barrel.  

Could you recommend a file and vendor? Because there are many different kinds of files. I assume that I should purchase the smallest one. Also, to even this barrel out like the stainless steel barrel seems quite ambitious. I don't even know if it's possible to make it as smooth and flawless as the stainless steel one. I thought the goal was more or less just to make the barrel window bigger so my ML packing can be used with it. Thanks in advance.

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The goal is to make the window bigger.  Bu you also have to clean it up and deburr it and remove sharp edges or it will cut up your packing rather quickly with use.

https://www.amazon.com/Needle-HIGHEST-QUALITY-Hardened-Strength/dp/B07KH8BG1F/ref=sr_1_16?dchild=1&keywords=jewlers+files&qid=1589372869&sr=8-16

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I ordered the files. However, I can't do much until they come. So I thought I would try to gather more useful information. Below is a link that shows the packing at its maximum dial up. Do you see anything wrong? 

https://drive.google.com/open?id=1fsmVrF8MOAvikayCnAP9txthuVRB2pVF

Also, why am I trying to make the window larger? I was under the mistaken impression that if the mound fits in the window, that means the aeg can accommodate that packing without further modification. How does making the window larger fix my problem? Thanks in advance.

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