Well matched straight arrows are the most important thing in consistant shooting. Without matching your arrows you really have no idea where the arrow will end up. 1 grain difference can send your arrow into the lower or higher scoring ring at 90m. A deserved 10 becomes a 9, an 8 becomes a 7 etc etc. The slower the bow the more critical this is, while the better shot you are the closer you also have to match.
Most arrow companies ship their arrows with advertised weight ranges. For example the Easton X10 is advertised as being within 0.5 grains, while some companies even claim 0.1 grains. This does not mean that your shafts will automatically come out this close.
Once you cut your arrows down to length, these numbers go out the window. It is vital that all shafts are weighed again. Points will also come out with variances, and this can be used to your advantage.
It is common for the shafts to end up within about 1 grain of each other. Then by matching the lightest point with the heaviest shaft you can get most of your arrows within 0.1 grains of each other. For example a set of X10's we built recently had a 1.1 grain variation. After matching the points to the shafts 9 were within 0.1 grains, and the other 3 very very close. This is good enough to keep all the arrows in the X ring at 90m. That's better than most can shoot, but at least that variable has been eliminated.
It you have an arrow which is wildly out then you will need to adjust the weight. This may require file the point down a little, or adding weight. A good way to add weight is to add hot melt (aluminium core arrows only) to the inside of the shaft. Once you are at the desired weight tip the arrow on it's point end and heat the point (avoid getting heat on the carbon). This will melt the hot melt to the glue and prevent it movinga round the shaft.
It is also worth checking your weights again after 3-6 months as use will wear them down and a once matched set can work itself into a 1 grain plus variance. In that case removing the points and starting again will often get them back within 0.5 grains.
