See if this helps, IBO speeds are the minimum specs a company can get away with. For instance IBO states that for every lb of draw weight your arrow must weigh 5 grains.(70lbs X .5 = 350) My bowtech shot 324 IBO but thats at the companys testing fac. with a 350 grain arrow, Nothing on the string etc...bare bow in other words. Now once you add peep, d ring, silencers etc the IBO(fps) slows down. No one shoots a IBO spec arrow b/c even thoug a 70lb bow with a 30 inch DL CAN shoot a 350 grain arrow it isnt good for the life off the bow, its almost like dry firing it in my opinion. Any way, IBO and FPS are the same, just that IBO specs are'nt realistic in the woods hunting. Once you add everything you need to hunt youll hardly ever reach IBO. ( I did reach IBO specs on my bow though) I just got lucky i guess.
GUYS if i am wrong on this please correct me, thanks