IBO/AMO speed?

[duranthas]

I shoot a Bear Code and have done this and that do try and eek out a bit more speed. According to the program I thought I was shooting in the 290ish range, but my chronograph said it was 275. When I checked the software again, if I switch from IBO to AMO velocity it seems to be dead on. Am I supposed to be going off AMO velocity, and if so what real purpose does IBO velocity offer?

[PSI]

The reason for the calculated VS chrono difference is that you probably haven't calibrated the program to your specific setup..

The Calibration Tab allows you to customize the program to your setup...otherwise, you are using "industry standard" values for arrow weight, draw weight, and draw length efficiencies.

Using the "default" efficiencies for a higher performance bow will usually result in higher than chronographed velocity being calculated.

You should also be aware that some manufacturers state IBO velocities in a range...like 315-321. So sometimes you may have to adjust the stated IBO velocity. The AMO radio button is for older bows that may not be in the database that were rated by that standard. Most companies don't give the AMO rating anymore, so it's there just for compatibility with old bows.