I believe that 310-318 is with nothing but a nock on the string. If you had a peep, and a WB then you definately would lose a lot of fps. My Birth Cert on my Tribute said 312 and I have run it through two different chronos. The firstone it was 308, 309, 311 and the second one it was 318, 319, and 322. I am sure the first one is much more accurate, but who knows. And actually who cares that much. I am sure the deer doesn't even notice the few fps loss or gain here or there.