ORIGINAL: gzg38b

When I used On Target, I found that my "predicted speed" versus my chrono'd speed was identical with my 365 grain "speed" arrows, and I didn't need to change the performance meter at all to get these results.

However, with my 515 grain hunting arrows, On Target predicted a speed that was 18 fps faster than the actual chrono. This was from the same bow, same setup, same tune, same wt on the string, same day, same chrono. Granted the KE was higher, but that's just due to the weight of the arrow. The gap between predicted speed and actual speed was huge with the heavy arrows and non-existent with the light arrows. This is where the performance slider comes into play, I believe.

With the heavy arrows, I had to slide the performance meter way down the scale just to get the predicted speed down to match the chrono. When I did that, those heavy hunting arrows went from being perfectly spined to overspined (according to OnTarget). I believe the results. It makes perfectly good sense that a launch speed of 18 fps slower would change the spine requirement of my arrows.

I think I would have got the same results with On Target if I'd just changed the IBO speed to get the predicted speed to match my chrono'd speed. Instead of using my bows advertised IBO of 316, I would have put in 298 for the IBO speed. The arrows that spined perfectly at a 316 IBO would have been overspined if I changed the IBO to 298, correct?

My trial version has expired, or else I'd try it to verify.