Here is 515.7 gr arrow. By the way the spine was at the top end of the Good area w/ a hunting setting. Oh, I think I've found your problem from your post on your bow. The program will select the CAM type for your bow. I made the mistake of changing it to 2 CAM hard and ran into a problem with actually VS predicted myself.

Thanks dave. I appreciate you taking the time.

I've actually chronod my bow with a 365 grain arrow. It was 297. This was real close to ON Target's prediction (within 2 fps).

If you read the edit to my other post, in bold, you can see what I think is happening. The chart below shows visually what I described in my other post. My bow is losing 7 fps for every 25 grains in arrow weight, not 5 fps like On Target assumes. That's why I'm so far off with heavy arrows.

If you notice, my bow was actually FASTER than the predicted speed for a 341 grain arrow. From 350 to 400 grains, it's pretty close. After 400 grains, the gap between predicted and actual just keeps getting bigger.

I am thinking that it has to be the info that is in the program for your bow. I've done the same thing with a friend's bow as I did my own and the program holds true. However, I've never tried an arrow that heavy. I've ordered a chronograph and will run a few different arrow weights through it this weekend and see what happens.

I setup my program for the 365 gr arrow at 297 fps (IBO of 309 fps)and get 265 fps for the 515.7 gr arrow.

Maybe you should contact Larry and see what he says about this. I had some issues that he helped straighten out.

Since a lot of guys are starting to ask about arrow selection I'm going to bumo this to the top. It lists everything we need to run your bow on a program.