I got this question as part of a larger issue from one of my Olympic Recurve students:
“My Arrow cut length is 29.25˝, so if I buy these new shafts should I cut them at 30.5˝ for now? Or should I cut them at 31˝?”
This student is working his way to a higher draw weight but wants to explore different arrows at the same time. Here’s what I said (with slight modifications).
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My standard recommendation is to make the draw weight change first, then fit yourself for new arrows. (Shooting to accustom oneself to a higher draw weight can be done blank bale and need only take weeks or at most a few months.) But the question here is basically: How do I fit arrows to allow for a higher draw weight in the future? So, that’s what I will address.
A start is to fit your current draw weight and cut length in the new arrow’s spine chart. Then move up one spine group on the chart (stiffer) and then add 1˝ to the cut length or move up two spine groups and then add 2˝ to the cut length. It all depends on how much draw weight you want to add. Roughly 5# = 1˝ of cut length, so if you are looking to go up five pounds, then you need just one spine group and one inch of cut length more than you are shooting now to allow for that change.
This is based upon how spine charts are set up by the manufacturers. They basically define spine groups, defining them by each inch of shaft length or 5# of draw weight for recurve bows. (There are some variations in the draw weights; Easton just made significant changes in their target recurve chart draw weights, for example.)
By buying an arrow that is stiffer, then cutting it longer you can create an arrow that is the same spine as the shorter weaker shaft that would be an exact fit. This arrow will shoot well and as you crank the draw weight up, you can shorten the arrows as you do so, keeping them reasonably well tuned. If you go up five pounds of draw weight and cut off that extra inch of shaft length, you have an arrow that is one spine group stiffer which is required at that higher draw weight.
Longer arrows than needed can also stretch the usable limits of a riser-attached clicker. While such changes are being pursued, using a clicker attached to one’s sight extension bar may be helpful. When arrows are cut shorter, the clicker needs to be moved in the exact amount of the cut.
This is a lot of fussing, but the advantage is this: it is very hard for archers to ignore where they arrows land. If one is shooting an untuned bow, the arrows will not group well and the archer will often think it is because they are doing something wrong and change their behavior for no reason other than their bow is not tuned. So having a reasonably tuned setup at all times can be beneficial.