AMO is the manufacturers trying to establish a standard for rating bow speeds. It' s the speed of a 540 grain arrow out of a 60 lb bow.

IBO was started (unsure by whom, maybe the IBO) where the speed is what a 70 lb bow will shoot a (I think) 350 grain arrow. That' s keeping in the safety standards of 5 grains of arrow for every lb of draw weight.

Anybody out there with better info, please post for crissmand.