figuring FPS

Discussion in 'Bowhunting forum' started by farmerman99, Dec 13, 2007.

  1. farmerman99

    farmerman99 Junior Member

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    Does anyone know if you can take, #'s of pull, length of pull, and weight of arrow and figure approx. FPS
     
  2. Holy Smokes

    Holy Smokes Senior Member

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    seems reasonable nuff
    I just ain't a mathmatictican
     

  3. J.C.

    J.C. New Member

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    yes, if you know the IBO speed of your bow.
     
  4. red44

    red44 Senior Member

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    Long winded, but I've seen 2 methods posted on other sites.
    #1
    start w/your bows IBO rating. (70/30 w/350 grain arrow)
    for every inch less in DL, subtract 10fps
    for every 5 lbs less (from 70), subtract 10fps
    for every 3 grains over (350), subtract 1fps
    for every 3 grains on the string, subtract 1fps
    #2
    shoot a group at 20 yards with the 20 yard pin, mark the center of the group
    do the same from 40 yards (using the 20 yard pin)
    the distance between the centers of the groups give approximate fps
    difference......approximae speed
    28.7.............220
    24.2.............240
    20.6.............260
    17.7.............280
    15.5.............300
    13.6.............320
    12.8.............330
    No idea how accurate these methods are, never tried it, but I did copy the info down for "some day".
     
  5. tnts79

    tnts79 Senior Member

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    There is a calculator on the internet that is very accurate. I can't remember the website, mabey someone else can??? I'm sure Bunnyman has it as one of his favorites! :p :lol: I just looked in my favorites and guess what?!!
    http://bucklemke.com/ke/ke.php
    I am shooting 280 through the chrono and this put me at 276... good enough in my book for a calculator!
     
    Last edited: Dec 14, 2007