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Over/under spine? And FOC

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    Over/under spine? And FOC

    Right now I'm shooting a goldtip velocity 340. They weigh 365 grains and I'm shooting them at 310 fps at 72lbs. I'm thinking about pitting heavier inserts in them to increase foc. The gold tip foc calculator shows 10.7% foc right now. Gold tip sells 50 and 100 grain inserts. If I went with the 50 grain I should be shooting a 403 grain arrow at 298fps and 13.9% foc. If I went with the 100 grain insert I should be shooting a 453 grain arrow at 282 fps with 17.3% foc. My main concern is would I be under/over spine with either? Is there any noticeable different between foc from 10%-17%?

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    #2
    You will some difference in mass. But just looking at foc. No you won’t see much till around 20%. So unless you’re wanting to go that high. Don’t worry about it. Build for mass.

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      #3
      The Easton arrow chart has adjustments you can make to see what added point weight does to spine (from memory it was something like +3 lbs draw weight for every 25 grains). Go calculate things on their chart making adjustments for bow speed, point weight, etc and see what arrow spine it says you need for that much point weight. If it says you’ll be underspined with an additional 100 grains, then I wouldn’t do it.

      D

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