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Thread: What does GPI mean?

  1. #1
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    What does GPI mean?

    Im shooting FMJ 11.3 GPI. What does that mean? Is it better to be higher or lower in gpi?



  2. #2
    grains per inch...just multiply number by length of arrow and you know how heavy it is.

  3. #3
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    GPI = Grains Per Inch. More grains means the arrow weighs more.
    PSE Source TT Smackdown Pro, B-Stinger,GT 55/75 Arrows, HHA OL-5519 Muzzy Trocar Broadheads, JBK Strings

  4. #4
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    11.3 grains per inch. Higher or lower in gpi means slower or faster arrow speeds from the same bow. It also means stiffer or weaker spine.

  5. #5
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    Quote Originally Posted by deadx View Post
    11.3 grains per inch. Higher or lower in gpi means slower or faster arrow speeds from the same bow. It also means stiffer or weaker spine.
    GPI has nothing to do with spine being weaker or stiffer. Example, Easton FMJ 340 has a GPI of 11.3 and a Easton Flatline 340 has a GPI of 8.2 .
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  6. #6
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    Quote Originally Posted by jwilson48 View Post
    grains per inch...just multiply number by length of arrow and you know how heavy it is.
    Yep! What he said. Has nothing to really do with spine. Just weight.

  7. #7
    As a general rule, arrows of the same model, from the same manufacturer, such as Gold Tip, will have a higher GPI with the stiffer spine, and therefore they do weigh more as the spine goes up. That does not neccessarily apply when comparing arrows between different manufacturers or even different model arrows from the same manufaturer.

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  8. #8
    Higher GPI arrows will weigh more at the same length. So more energy, less speed, but probably in the end more penetration. FMJ's are getting up there as far as weight goes.

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