Whats the formula to figure out GPI?

[whitetailtrail]

Just looking for advice


Thanks!

[Pistol]

No less than 5 grains per pound of draw weight is the rule of thumb. I am sure Rocky will chime in and his advice is good.

[jerp]

Are you asking how to figure GPI or what is the best GPI? If you go to a website that sells arrows it will list the weight of all the shafts and components - inserts, nocks, vanes - just a matter of adding it up. Not sure about all brands but Beman prints GPI right on the shaft.

[PSD Ryan]

If you are trying to find the gpi of your current arrow and don't know it, consult manufacturer specs or calculate it by obtaining bare shaft weight (shaft weight = total weight - broadhead, insert, nock, fletchings, wraps), and dividing by the shaft length, not finished arrow length (subtract about 1/2" from finished length, or just measure)

If you are trying to find out what gpi to use, it's more a balance of what you're going for, and sometimes takes some expierimentation. KE vs speed vs momentum all starts playing in. With your low draw weight, it becomes more of an issue because you don't want to reduce any of those aspects too much, but you have to stay above 5 grains per pound of draw for total weight to avoid damaging your bow.

[whitetailtrail]

Thanks!