Weight reduction and speed change

[Olink]

If I lose 10 pounds of weight how much faster will I be able to run?.... Only kidding guys... But really, I'm having trouble remembering the general rule and I can't seem to find the answer in any searches... What I really would like to know is if a bow has an IBO rating if 335, how fast would it shoot the same arrow at 60lbs of draw weight?

[BGfisher]

IBO is rated at 70 lbs. If you shoot the same arrow weight at 60 lbs you should lose about 20fps. My chrono usually shows about 2fps difference per pound. Depending on bow efficiency it could be a little more, a little less.