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#### Busterbrown

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Is there a calculation. Or could someone give me an educated guess. I shoot an elite tempo 70 lbs DW. 32 “ DL. I’m shooting a GT hunter Xt 300. 9.2 gpi. Finished arrow 455grs. Shooting 300 fps. Question??? If I went to an x cutter or something similar at 7.2 gpi. How much speed would I expect to gain???

#### The Old Guy

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Try backcountrybowhunting.com and plug in your numbers. These sights tend to be faster than actual chrono speeds.

#### azscorpion

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http://backcountrybowhunting.com/calculator/

I ran the numbers for you according to IBO on that bow, you will gain about 15 FPS, depending on the cut length of arrow, I figured 50 grain drop in weight

#### FrogKicker

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I was looking for a calculator like that. Thank you.

#### rapids

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For a quick calculation, I’ve used that for every +/- 5 grains of arrow weight, you will loose or gain 1 fps.

#### 5MilesBack

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Every bow is different as to what that average gain or loss will be across a large range of arrow weights. But for my bows 1fps for every 3.5gr of weight seems to work out the closest to reality with chrono speeds. So I'm guessing about a 30" arrow length for you and 2gpi lighter, so 60gr divided by 3.5 equals 17fps........or thereabouts.

#### merlinron

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generally speaking,...the 1fps for every 5 gr. weight is about right, of course that was established quite a while ago and bow speeds have generally increased since then, so you might see a bigger gain in speed. the other thing to consider, is that today's cams are pretty harsh on the arrows and getting too light ( getting too far outside the "spine box", might give you some pretty wild flight.

#### Busterbrown

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Thanks. I am thinking of shooting IBO. was wondering if it would make enough difference to be worth it.

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