GRAINS PER INCH
The Grains Per Inch, or GPI, determines the
weight of the arrow *key item* BEFORE any
inserts, nocks, or fletches have been added.
While this isn't my top priority when selecting
an arrow, it is still a very important component.
The weight of an arrow determines many things.
First and foremost, it is an important factor to
make sure that your arrow conforms to minimum
standards put forth by bow manufacturers, and
also to be sure that your arrow meets the legal
arrow weight for hunting. It also affects the
velocity and momentum of the arrow, and helps
determine how much point weight you will need
to maintain the correct dynamic spine.
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INTERNATIONAL BOWHUNTING
ORGANIZATION
Most bow manufacturers use the International
Bowhunting Organization, or IBO, standard of
5 grains of arrow weight per pound of draw
weight as a minimum arrow weight for warranty
purposes. They also use that same standard to
determine the fps rating - 30" draw length, 70