I was disappointed with my speed also when i sent an arrow through the crono. My bow is rated at 302 and i clocked in at 240. I did this shortly after buying my bow new and i looked at the guy working at the shop that i bought the bow from and he told me that those numbers are rated with out string silencers, peep sights, and at full poundage and draw length so those are some things to look at also.