[WhitehartFB]

This and the nocks as OB said really do make a difference another tip if you are prepared to take this much care of your arrows and matching them up is to clean the inside of the shaft with a pipe cleaner sometimes there is quite a lot of muck inside.

When shooting the bareshaft it is also a good idea to shoot at a distance where you are normally assured of tight groups and be honest about how good a shot was otherwise this will drive you potty and scew up your results.

Finally during the season it's worth doing the same with your fletched arrows things change over a season and this way you will find any rogue arrow that has started to refuse to group it might only be half a colour different but that could be 24 points over a FITA. Target plot or any software that allows you to plot arrows and identify the arrow number is good for this.