Rob is correct.......although I'm pretty anal about all my arrows for both hunting and 3D weighing very close to each other in reality for practical hunting 3D distances we couldn't tell.

I was talking with a very reputable employee of a popular arrow manufacturer and a darn good shooter about this earlier this year. He told me that it would be very hard to tell the difference even over 20grs different per arrow unless you shot them from a machine at about 30 yards.......and even then they will still cut the original hole just not quite in the center of the first.

Where weight tolerances really show up is in long range shooting field/fita type stuff.

I still try to get my weight tolerances as close as I can, especially for 3D shooting but I put more emphasis on straightness and spine tolerances......fortunately all 3 of these qualities generally go hand in hand with the quality of shaft you choose and some are "guaranteed" to be withing a certain range within the bundle.
Most of the time anyway.

It sure doesn't hurt to go over every shaft with a fine tooth comb for tolerances and in a perfect world we could stand there and sort through an entire lot with accurate equipment and pick and choose our own......unfortunately we're stuck with the crap shoot that is arrow shaft buying.
That's why I always buy the best quality shafts I can , look them over hard and hold a manufacturer to any tolerance guarantees on bum shafts.