How are speeds determined?
There are two standards by which speed is measured, IBO ratings and AMO ratings. IBO stands for International Bowhunting Organization. IBO testing uses a 70# draw weight, a 30″ draw length and mandates the 29″ arrow be 5 grains of weight per peak pound of draw weight. So, IBO speeds are obtained using a 350 grain arrow (70#’s of draw weight X 5 grains per pound). AMO (Archery Manufacturers Organization) speed standards use a 60# draw weight, a 30″ draw length and a 29″ arrow at 9 grains per pound of draw weight. So, in AMO you’re testing with a much heavier arrow at 540 grains (60 # draw weight X 9 grains per pound). Speed testing is generally performed using a mechanical shooting device such as a Hooter Shooter which maintains consistency between each shot and eliminates human influence on the shot.
