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Thread: How to grind down .750 on/off pin?/Serious shootdown with emag onoff in classic valve

  1. #1

    How to grind down .750 on/off pin?/Serious shootdown with emag onoff in classic valve

    Well, I put the on off pin and an x-valve on/off assembly into my classic valve. yes, it did make the trigger pull much lighter.

    Unfortunately, it resulted in serious shoot down. Can't figure that out.

    Anyways, I figure I can either figure that out, or grind the pin down to .712 for my emag valve. What is the best way to grind that down so that there are no burs, or what is causing that shootdown?

  2. #2
    Can you describe what you observed that you're calling shootdown?

    As far as grinding the pin, if you do have the gray grinding wheel (usually comes standard) with a Dremel tool, use that with a pair of needle-nose pliers to hold the pin. It will likely get hot. Just grind flat, and when you are getting close to your desired length put the pin at an angle to smoothe out the sharp edges a tiny bit. The gray wheel isn't very coarse, so I didn't get any burrs when doing it that way.

  3. #3
    While shooting the trigger pull became noticeably lighter while the sound coming from the barrel became noticeably quieter.

  4. #4
    I think you may have an issue with air getting to the valve. Not the valve its self. When I first set up my pneumag I had a classic valve and I could rip it with and rtp/emag on off. And it had a .750 pin length (that's factory length in the classic)

    Also, have you shot.this over a chrono? Or are you assuming its shooting down just by sound alone?

  5. #5
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    I have never made mine shorter than .740 on similar set ups. Trigger pull is noticeably lighter and the velocity is good.

    "I'm not happy unless you're not happy"

  6. #6
    Don't know what changed, but now it's just chuffing if I fire it faster than 1 bps. I am using a classic valve with level X that is tuned, at least for the regular on off.

  7. #7
    Check the trigger rod length, make sure a credit card width gap is behind the trigger.

    Id try one size larger carrier with no shims on the lvl 10 as well.

    Mine had similar issues, the carrier change fixed it. Remember to use the same carrier o ring
    Last edited by Cokrkilr; 04-02-2013 at 03:09 PM.

  8. #8
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    Quote Originally Posted by halB View Post
    Don't know what changed, but now it's just chuffing if I fire it faster than 1 bps. I am using a classic valve with level X that is tuned, at least for the regular on off.
    If the level 10 is properly tuned for one on-off it should work for the other unless you are getting a leak in your on-off. You can check the on-off orings by holding in your trigger. If the pressure continues to increase to the point where it pushes the bolt forward and can vent air, then the on-off is leaking. If it doesn't leak or just weeps a bit and then stops, then the on-off is fine. It sounds like it might be choked for air as mentioned.

    Is it resetting immediately following a shot (ie; is the bolt reset and the trigger coming fully forward)? If the trigger rod is touching the trigger even in the forward position, then it could interfere with the recharge of the valve.

    Is the bolt spring new?
    Except for the Automag in front, its usually the man behind the equipment that counts.

  9. #9
    Bolt spring is about 5 years old. I tried different springs from the kit. Same problems. Changed the carrier, same problems. Chornoed it, same problems.

    I think at this point I'm jsut going to grind it down so I can use it in my emag.

  10. #10
    I've tried it in two other classic valves, both with level 7. Same thing. Putting the on off seems to drastically lower the FPS, turn it up, still get the chuffing.

  11. #11
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    Put two level 10 shims in between the two on-off halves. It will simulate a shorter pin and give you an idea if that is the problem.

  12. #12
    BINGO. Yes, now I can rapid fire. However, I am hearing shootdown. Not as bad as when this all started, but still shoot down.

  13. #13
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    That is an indication that you are headed in the right direction. For whatever reason, your setup needs a shorter pin.

  14. #14
    But the pin IS an x-valve or rt pin. I calipered it at .75 (calipers only go to .01", which is why I'm scared to grind it down, however, if the problem doesn't get resolved by tomorrow morning, I'm grinding).

    I thought putting a .75 pin with an x valve assembly into a classic valve was rather straight forward.

  15. #15
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    Use a file. And file till it is 0.74. And by 0.74 I mean. Till it just no longer shows 0.75. My classic minimag would not cycle at all till it hit .075. And I started with it at .769.

  16. #16
    Okay. I can accept that this needs to be done. But I need to know WHY it has to be done. Tom Kaye is a god. I can't imagine why the pin that he designed for an RT valve won't work in a classic valve with the proper on/off. I know all sorts of people drop it into their set ups. Why are my three valves different? (Odds are it is this on/off that is different, I doubt any differences could be found amongst these three valves)

  17. #17
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    Why ask why. I couldn't believe 2 100ths of an inch kept my gun from cycling. But you can look up my minimag thread from a month or so ago. And that was the result of my fight to get my wife's gun to work. Stock rt on off and pin in a classic mag. Pin was .769. It would not cycle at all till I got to .75. Then it worked fine.

    My best explanation to the minuscule change in gun valves is the tiny variation when they mill the on off hole in the valve body. But I can't really tell why.

  18. #18
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    You have three valves that don't work with this pin. Did you use the valves in the same gun/body/rail? Do you have the rail bushing installed?

  19. #19
    Tried it on a ULE body, tried it on my body that's worked for years and years. Tried it on a new rail/sear, tried it on my trusted rail/sear. Yes, had the bushing installed. (found out how important that one is because I'm trying to get rid of bolt stick on one of these classic valves, but one problem at a time.)

    Maybe we should start from the beginning. Am I supposed to use everything from the x-valve assembly? The upper and lower housing, the o rings, including the quad 004?

  20. #20
    Quote Originally Posted by halB View Post
    Tried it on a ULE body, tried it on my body that's worked for years and years. Tried it on a new rail/sear, tried it on my trusted rail/sear. Yes, had the bushing installed. (found out how important that one is because I'm trying to get rid of bolt stick on one of these classic valves, but one problem at a time.)

    Maybe we should start from the beginning. Am I supposed to use everything from the x-valve assembly? The upper and lower housing, the o rings, including the quad 004?
    On my first X-valve, I couldn't get the thing to rapid fire at all with a .750 pin. I had to go shorter.

    If you're not using Emag lowers, you can replace the quad o-ring with a 006 urethane o-ring. And if you are using Emag lowers, your pin is way too long anyway (should be .712).

  21. #21
    Classic rail (choice of 3), powerfeed body/ule, intelliframe/cf frame/homemade frame.

  22. #22
    I guess we'll never know. Last thing i did was I changed out the quad o ring for the 006 teflon, and there was about as much improvement as when I put the spacers in there. I then ground the hell out of it, to a flawless .712 or .713, using a dremel. Thanks Justus, it was pretty easy once I had the confidence.

    Put the pin in my emag valve, and I believe it is working. Seem to be getting some bolt stick when shooting fast, but whatever, my tank only had 500 or 600 psi in it. Just wanted to make sure it didn't leak. Once I fill up my tank I'll let you know how it's doing.

  23. #23
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    Quote Originally Posted by halB View Post
    Maybe we should start from the beginning. Am I supposed to use everything from the x-valve assembly? The upper and lower housing, the o rings, including the quad 004?
    All on-off parts need to be transferred to the classic valve. The quad oring can be changed out to the urethane oring. The quad oring requires the use of a shorter pin.

    If you use the quad oring in the emag, use the 0.712" pin length. It will work fine in the classic like that as well.

    You will get some shootdown and chuffing with low pressure from the tank. The level 10 operation requires a higher input pressure to the valve in order to work properly.

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