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Thread: RT Pro on/off pin length?

  1. #1
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    RT Pro on/off pin length?

    so, according to this tolerance thread, the RT Pro on/off pin should be .765", whereas the ReTro, classic RT and X-valve are all .750".

    why is that? is this information accurate?

  2. #2
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    Quote Originally Posted by Cyco-Dude View Post
    so, according to this tolerance thread, the RT Pro on/off pin should be .765", whereas the ReTro, classic RT and X-valve are all .750".

    why is that? is this information accurate?
    Keep in mind the rail heights.

  3. #3
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    My classic rt has a .744 on off pin in it. I've never manipulated it. And its not broke. That is how it came from the factory. My RTPro does have a .750

    I checked them recently because in the last 14 years I've not found a rtpro valve that RTs like my classic rt with the same bottle. So I decided to check my classic rt and my wife's RTPro. The pin length is the difference.

  4. #4
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    Quote Originally Posted by Dayspring View Post
    Keep in mind the rail heights.
    my rt classic and rt pro rails have the same height; ~.415.

  5. #5
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    I could be wrong but I thought the shorter pins were replaced with longer ones to extend the life of the sear.

  6. #6
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    Quote Originally Posted by smilestyler View Post
    I could be wrong but I thought the shorter pins were replaced with longer ones to extend the life of the sear.
    Probably a little. The shorter pins also makes them RT at lower pressures. Which in turn makes them rt faster at higher pressures. I'm still running the same sear that was in the marker when i bought it off its original owner in ???99???. Couldn't even guess how many cases have been fed through that gun. Was doing a case a week in it back in 01-02. 03-jan13 it sat dorment. I've probably put 7 or 8 cases through it in the past year.

  7. #7
    I'm not seeing how pin length is going to affect sear life. All other things equal, it has the same top force, translated to the sear, regardless of length. The pin is the hub of the three parts (sear, reg, dump chamber) of the firing system and as such effectively times the firing system. Longer pin reduces reactivity and moves toward the starvation end of the spectrum and shorter pin increases reactivity and moves toward the runaway end of the spectrum. But top force is top force.

    If there is something missing here, I'm listening closely.

  8. #8
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    Years ago you could buy from AGD , Tuna, etc the shorter pin. Then all of a sudden they wouldn't sell them. Maybe ask Tuna the why and you have your answer.
    Since mags seem to be engineered to last 100 years one possible reason for he change is the wear to the sear that occurs in an insanely reactive trigger.
    But again, I couldbe wrong too. It was a long time ago.

  9. #9
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    Quote Originally Posted by smilestyler View Post
    Years ago you could buy from AGD , Tuna, etc the shorter pin. Then all of a sudden they wouldn't sell them. Maybe ask Tuna the why and you have your answer.
    Since mags seem to be engineered to last 100 years one possible reason for he change is the wear to the sear that occurs in an insanely reactive trigger.
    But again, I couldbe wrong too. It was a long time ago.
    Was thinking the stop on selling them in the classicRT was right before forcefed hoppers really took ground. I had been told it was to make the markers more controllable from out shooting the hopper. Back in 02 nobody at the field I played at would use my marker. They couldn't keep from blending paint with it. Marker was my trusty classicRT with .744 pin. 1000-1100 psi input from a nitroduck megareg. And a intellifeed linked 18v revolution. Anything more than a 5 round burst was blender city. I could single shot. And 3 round burst all day long with it though.
    Last edited by blackdeath1k; 06-08-2014 at 04:32 PM.

  10. #10
    Quote Originally Posted by smilestyler View Post
    Years ago you could buy from AGD , Tuna, etc the shorter pin. Then all of a sudden they wouldn't sell them. Maybe ask Tuna the why and you have your answer.
    Since mags seem to be engineered to last 100 years one possible reason for he change is the wear to the sear that occurs in an insanely reactive trigger.
    But again, I couldbe wrong too. It was a long time ago.
    Tuna has always sold, and continues to sell, all pin lengths from .712-.770 to this day, and to the best of my knowledge, this has never changed.

    http://www.tunamart.com/index.php?c=39&p=108

    As for the sear, RTing causes no more wear than slow shooting, shot for shot. That was a myth that existed back in the early days, when people thought the RT effect was a kind of loosely controlled runaway condition or something akin to valve float in internal combustion engines. But those were mistaken notions, long since dispelled. The only increase of wear comes from simply firing more shots in a given time frame.

  11. #11
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    The original RT Pros came with sears that had hardened carbon steel attached to the top of the sear where it catches the bolt. It was hard to prevent wear on top due to the increased rotational force placed on the sear by the on-off, but was more prone to impact damage because it was more brittle.

    A shorter pin allows the valve to charge before the sear is fully engaged on the bolt. On level 7 bolts, the forward force is quite big. So, if you got the valve going reactive you repeatedly slammed the edge of the bolt against the edge of the tip on the sear causing it to fracture and because the sear was extra hard, it also damaged the lip of the bolt. This was solved by installing longer pins that allowed the sear tip to be farther up on the bolt lip before the on-off opened to allow air into the chamber to push the bolt forward. This spread the force over a larger area and prevented sear and bolt damage.

    Going back to the original sear design allowed the sear to be less brittle and the wear issue on top wasn't so much of a problem anyway, so it allowed the use of the original 0.750" pins again. The level 10 bolt further prevents sear tip wear. Shorter pins will still cause the sear to wear more than a longer pin, but not at a catastrophic rate. Its more of an acceptable wear level since the sear is a long term consumable part anyway.
    Except for the Automag in front, its usually the man behind the equipment that counts.

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