HuntingBry, I'm curious as to your setup. I'm almost identical to you except I'm shooting a 370 gr arrow and my speeds mirror yours. This of course is unless the chrono is off. I did however have mine turned back to 63lbs when I did this.

One thing I never realized and you guys might all laugh at me, but speed really depends on how far off of IBO spec you are. If you keep your arrow at the 5gr per pound, you'll get pretty close to what the BC says. My arrows are around 5.4 gr per pound and am getting well under what I expected. Now if I cranked that bugger up to 70 lbs, I should be closer to the 290ish mark I would think. My BC was 70.6lbs, 28" draw 350gr arrow @ 305fps