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Old 10-03-2017, 08:27 AM   #1 (permalink)
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RT tuning help

Despite furiously googling mcb and AO threads, I haven't found the answer I seek. Here is what I'm working with for anyone who wants to offer guidance.

ULE body
Lukes rail
Standard AGD composite frame
Retro valve with Level 10, working pretty well.
850psi output HPA

I have .712, 728, 740, and 750 on/off pins. I have urethane on/off top orings and buna(?) quad orings, as used in the emag.

I want the gun to bounce when I want it to but still be controllable.

At the field sunday I found the urethane ON/OFF oring with the .712 on/off pin mostly achieved this. However, it seemed like the trigger rod would not reset consistently. Sometimes it will stop short. No leak but it's not sticking out as far.

I get less RT effect with longer on/off pins, but the trigger rod resets better.

With the quad oring the gun shoots full auto regardless of what pin I use. Ie if I hole the trigger it continues to fire. When I release the trigger it stops. Good for a giggle but not what I'm going for here.

So, is this result with the quad oring normal? I found older posts where people claim to use the quad oring in their mechanical mags but for me the gun doesn't function properly. Will the urethane oring break in and function better? Only one way to find out I guess, but I'm out of air now.

Last edited by uglyduckling; 10-03-2017 at 11:59 AM.
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Old 10-03-2017, 11:15 AM   #2 (permalink)
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rt is the result of a few things.

pin length
tank out pressure ( This becomes 2 categories)
how broken in the orings are

generally i don't go under .740 unless it is an emag. I don't use quad orings unless its an emag. Oil makes a significant difference in a mag. In order to break the orings in you need to condition them similar to a baseball glove. oil and use break them in.

Tank pressure. not all tanks are equal i have found that 850psi and fast recharge rates matter. If you have multiple regs setup with the same pressure they will behave slightly differently.

what tank reg are you running?
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Old 10-03-2017, 11:35 AM   #3 (permalink)
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Quote:
Originally Posted by uglyduckling View Post
So, is this result with the quad oring normal?
No, that says that the o-ring isn't working (sealing) at all. The lower lip on a quad o-ring is about 0.020" lower than the middle of a standard oring, which is why they need the shorter pin to start with. They are more finicky and weaker than a standard urethane o-ring, so don't go that route until all else fails.

This is an RT type valve to start with, correct?

[Adding on to superman] Part of recharge rate is flow from the bottle reg to the valve. Some ASA's press the bottle reg pin in until the plunger sits on the face of the reg, blocking the flow. Sometimes you can back off a screw knob on an ASA and get better RT. Some 90 degree 1/8" NPT fittings can also block flow when the male end of the hose bottoms out in the fitting.
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Old 10-03-2017, 12:11 PM   #4 (permalink)
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Awesome information thank you both!

Quote:
Originally Posted by superman View Post
what tank reg are you running?
Ninja pro reg. Tank had avout 3500psi at the start of tinkering.

Quote:
Originally Posted by Spider! View Post

This is an RT type valve to start with, correct?
Affirmative. Retro valve.

I test fit four different new quad rings on my on/off pins and chose the one that fit tightest, but even that one was loose compared to the urethane.

Sounds like I just have some more breaking in to do. I have used copious amounts of autolube and will just continue that.
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Old 10-03-2017, 01:24 PM   #5 (permalink)
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Originally Posted by uglyduckling View Post
Sounds like I just have some more breaking in to do. I have used copious amounts of autolube and will just continue that.
Also, check that the trigger and sear don't bind or drag on their pins. The internal o-ring on the on/off can get neglected with little or old lube.
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Old 10-03-2017, 02:37 PM   #6 (permalink)
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Sear and trigger seem to move freely. The internal on/off oring is a snug fit to the shaft of the on/off pin.

Quote:
Originally Posted by Spider! View Post
No, that says that the o-ring isn't working (sealing) at all. The lower lip on a quad o-ring is about 0.020" lower than the middle of a standard oring, which is why they need the shorter pin to start with. They are more finicky and weaker than a standard urethane o-ring, so don't go that route until all else fails.
I want to revisit this part to better my understanding...

Are you saying that the on/off pin needs to be shorter in order to work with this setup?

I'm staring at this to try and understand how moving the point at which the seal is created affects things.

https://www.zdspb.com/media/tech/anim...emag2_6fps.gif
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Old 10-03-2017, 02:38 PM   #7 (permalink)
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Quote:
Originally Posted by uglyduckling View Post
Sear and trigger seem to move freely. The internal on/off oring is a snug fit to the shaft of the on/off pin.



I want to revisit this part to better my understanding...

Are you saying that the on/off pin needs to be shorter in order to work with this setup?
This is why you use a .712 pin with a quad oring in emags.
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Old 10-03-2017, 02:48 PM   #8 (permalink)
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I did try the .712 pin and the result was full auto
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Old 10-03-2017, 02:50 PM   #9 (permalink)
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you also are not using an emag though.
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Old 10-03-2017, 03:01 PM   #10 (permalink)
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Well, yes but I wasn't sure if that mattered.
So it sounds like the quad ring is just not meant to be, at least for my particular gun. I'm just going to try and put a case through it next weekend and see where that leaces me. I had fun shooting it on sunday

Thanks for your help, cleared things up a bit!
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