You're right you should be getting more than that. I was getting 265fps with 330 grain arrows at 25.5". My short little arms are only putting out 20fps less than you, which shouldnt be. The only thing i can think of either your arrows weigh more than you think or the chrono was off. The only thing i can think of is taking thesilencers of and buying a string supressor so it isnt gaining noise without the silencers.