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Thread: An easy way to improve efficiency

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  1. #1

    An easy way to improve efficiency

    I still see quite a few posts complaining about Mag efficiency. This seems funny to me because I thought this was all settled years ago. While RT based Mags will never be able to "shoot to the bottom of the tank" there is a very easy, though not very fashionable, way to improve efficiency:

    10" un-ported barrel.

    I just picked up a 10" fibur from Deadlywind and requested no porting. First time testing it and on top of being inordinately loud, it chrono'ed at 340fps. Last time I had the marker out it was sporting a Freak with the first porting about 6" down the barrel. Having no porting for the full 10" allowed me to back the velocity adjuster way out to get back down to 280.

    Apologizes to the large percentage of this community that already knew this. It's apparent that many people do not. The ball stops accelerating at the first port in a barrel. That means that barrels with porting at 5 and 6 inches need a much higher volume of air to get up to speed. No Porting = Longer Effective Length = Less Air Needed = Higher Efficiency. Of course people that don't like their marker to sound like a hand cannon can achieve the same effect by using barrels that have longer unported sections.

    TK recommends 8-10 inches. His original thread discussing this can be found here:
    http://www.automags.org/forums/showt...ncy-Tech-Tip-1

  2. #2
    Join Date
    Sep 2004
    Posts
    1,155
    with a healthy underbore, i get an acceptable 1200-1300 out of my mags.
    loose cars and fast women

  3. #3
    Quote Originally Posted by cockerpunk View Post
    with a healthy underbore, i get an acceptable 1200-1300 out of my mags.
    "Healthy underbore" meaning a difference of -.004" or greater?

  4. #4
    Quote Originally Posted by AGD
    So as far as our guns are concerned, the best efficiency would be had with an 8-10" effective length barrel. Since two piece ported barrels with an effective length of about 5-6" are the rage right now you hear a lot of complaints about gas efficiency. Under some circumstances there is a good reason to use a short effective length barrel. Short barrels cut off the acceleration abruptly by venting and this has the effect of tightening up the shot to shot velocity variation. If you need this at the expense of efficiency then go ahead. Tighter velocity control usually translates into some improvement in accuracy due to better consistency.
    So my underbored FLASC kit, which has a 9" control bore followed by 3" to 5" of porting, seems ideal. 9" effective unported length, followed by a section of porting to vent and effectively tighten up the consistency.

    Good to know.

  5. #5
    Join Date
    May 2009
    Location
    nj
    Posts
    785
    This is why there has been some tape covering porting on my barrels since i don't remember when. Plus i like them a little louder.

  6. #6
    Join Date
    Jan 2002
    Location
    southern IL
    Posts
    1,887
    Quote Originally Posted by sjrtk View Post
    This is why there has been some tape covering porting on my barrels since i don't remember when. Plus i like them a little louder.
    Only issue with the tape is if you break a ball in there. Harder to clean out the ports from paint oozing back in the barrel.

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