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Porting and velocity?

Discussion in 'Shooting Related Threads' started by Sargon, Aug 19, 2009.

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  1. Sargon

    Sargon TS Member

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    Has anyone done an actual testing on how porting affects velocity? I am sure it reduces it some but was wondering how much. I have been told that it reduces effective barrel length to that of the porting. For example if you have a 32-inch barrel and the ports are centered around 27 inches that will be effective length of barrel as far as its ability to generate velocity. Any truth to that?

    Please let not make this a I hate porting, it ruins a good barrel or what a waste of money thread.

    Thanks,

    Mike
     
  2. EuroJoe

    EuroJoe TS Supporters TS Supporters

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    Powder is burned up in 22", porting is to reduce bbl. bounce, not recoil.
     
  3. Neil Winston

    Neil Winston Well-Known Member

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    Barrels vary, one to another and unpredictably, in the chronographed shot speeds they produce.

    Though I've looked, I've never seen evidence that ported barrels, generally, produce less velocity than a similar unported barrels, taking into account they vary anyway.

    Neil
     
  4. Bill Bauer

    Bill Bauer TS Member

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    Listen to Mr. Winston, he's right on the money.
    Bill
     
  5. JACK

    JACK Well-Known Member Supporting Vendor

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    What size bit do I use in my Makita?
     
  6. Conn. Man

    Conn. Man Member

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    MIA,

    3/16" LOL.
    Sandy.
     
  7. Sargon

    Sargon TS Member

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    I posed this question to Ron Reiber, Product Manager from Hodgdon and asked him if max velocity is reached in the first 20" of a barrel. He said that all their load data (velocity) were based on a 30" barrel and you can add around 15-20 fps for every inch added or subtracted if shortened. He also said that porting will cause the effective length to be shortened.

    That is why I asked the question here. It makes more sense to me that after 20 or so inched of a barrel the velocity should remain the same if not decrease due to friction. So a ported barrel should not affect the velocity either.
     
  8. timb99

    timb99 Well-Known Member

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    Even if the powder is burned in the first 20 inches or so of barrel length, it doesn't necessarily follow that after that point there's no longer any gas pressure pushing on the back side of the wad.

    The wad/shot are still being accellerated all the way to the end of the barrel by the gas pressure, which is why Mr. Reiber said what he did. Longer barrel, more time to accellerate, higher muzzle velocity.

    If you took an unported barrel, tested the heck out of it with some very carefully created test loads, then ported the barrel and retested with exactly the same test loads, you may find a difference.

    But in the end, it still wouldn't matter all that much.
     
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