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Thread: High failure rate of PMR bolts

  1. #21
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    Quote Originally Posted by Lurker27 View Post
    My guess is that it's because of the way their geometry is laid out, the breech pulse acts on the bolt significantly. Couple this with a ton of static friction (they add something like 5 thou crush to the main seal at rest) and it amounts to effectively decaying force during the stroke. Bad lpr or solenoid flow would make this a lot worse. Plus you have an air spring that basically works exponential in throw, but the flow of the orifice is only linear in pressure. I'm not sure if the air springing is coming from residual front volume or blow back.

    There's a similar phenomenon in both the gamma core and paragon with the return of the bolt. Sizing of orifices becomes very important to balance bolt speed (orifice plate/ restrictor) and oscillatory behavior. Having a 2 or 3 stage system as both of these guns do allows you to skew way to the side of fast final bolt speed.
    Sorry, don't understand what you mean in that last para. Gamme core has similar phenomenon? As in it has bolt bounce on bolt return?

    The original fore-barer of the gamma prototypes had front of stroke bolt/main valve bounce. It was a relatively easy fix though.
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  2. #22
    Insider PBSteve's Avatar
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    Yeah I don't know what he's talking about either, like you said easy to avoid in a gamma core.

  3. #23
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    I'm very poorly trying to say that a system optimized for bolt velocity by sizing the orifice and geometry may not be optimized for latching forward. And that the elegant thing to do is to decouple the requirements by having multiple bolt stages.

    In the case of the gamma core, I'm guessing you increased the orifice linking the main chamber to the bolt front to eliminate oscillation/bounce.

    That increases final bolt speed, and bolt momentum, and you don't build excess pressure at the bolt sail once the volume reduction in the air spring begins to be a relevant term to the final pressure.

  4. #24
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    You would probably be right Ryan. The good part is that stage 2 is tunable as well and quite small so you have pretty ideal control over that dynamic.



    This my favorite review Gordon ever did:


    Arguably the OG deftek. So many fricken strange engineering "features" in paintball with people solving problems that aren't actually problems. PMR, the omen, ATS (would be fun to adapt a rainmaker with the reset lever), etc

  5. #25
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    Quote Originally Posted by Lurker27 View Post
    In the case of the gamma core, I'm guessing you increased the orifice linking the main chamber to the bolt front to eliminate oscillation/bounce.
    There are at least 3 ways (off the top of my head) to avoid it in the gamma core system, I don't think that's how I'd do it.

  6. #26
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    Increasing that hole seems the most reliable and predictable way of doing it. It seems to me to be the most logical. What would be the other 2 ways?

  7. #27
    the OG deftek was the automag powerfeed.

    also jack, confirm or deny, the deftek was because someone missed a mm somewhere in the CAD/CAM in the 05 ....
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  8. #28
    Insider PBSteve's Avatar
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    That seems like a pretty unlikely mistake

  9. #29
    Sounds like one of those silly rumours like the one of the barrel being mounted at an angle.

  10. #30
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    Meh, I guess you could count the mag, but take away the flaps and the omen had the same type of deftek.

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