Um, you would be suprized.
A new set of high end arrows would often have a 1 grainvariance between the set. The points could be the same. This could lead to a +/- 2 grain variance in a set. (I have build X10's that would have been +/- 3grains had I done it randomly)
So for a 2 grain variance on a
compound bow with a speed of 265fps you would get a 24mm difference in impact point at 70m. For an average shooter (325 at 70m scorer) this will impact on the score for that shooter.
90m and that would be a 42mm drop. That's huge! Will keep you under 300 at 90m which is out of 1300.
For
recurve the bow is slower so the impact is greater.
For a 195fps
recurve bow with the same weight variance that 2 grains will make a 68mm difference in impact at 90m and a 39mm difference at 70m. Enough to impact on the scores of even a 1000 recurve shooter.
How to weight match correctly
Go out and buy some grain scales, make sure they go to 0.1 of a grain. (many are only 0.2 or 1.0)
Cut all your arrows to the exact same length
Weigh all your shafts once they are nocked and fletched
Weigh all your points
Match the heaviest point with the lightest shaft
That should get around 9 of the dozen exactly the same.
For the others if they are far out ( > 1 grain) then either file the point if to heavy or add tin foil to the shaft for too light.
Re weigh after gluing in point and they should all be well within 0.3 of a grain.
For 1 hour's work you may pick up ALOT of points.
Well it's best to completely eliminate as many variables from both equipment and shooting form as possible, However it's so easy (I know) to fill your head with problems that aren't really that much of an issue, I have heard of archers weighing individual components of arrows, filling piles down (without anaesthetic) even trying to presicely match the amount of hot melt glue used on points, Who can shoot so well that that's going to make a difference ?