It is good to weigh your arrows and components but adding six grains to the arrow wouldn't make an inch of differance at 50 yards. Especially with todays fast bows.

If they all weigh 106 grains then be happy. I've seen some broadheads weigh anywhere from about 93 grains as a low to 107 grains as a high. Of course these were cheap-o broadheads but.....

I'd be willing to bet you dollars to donuts that there is more than a 6 grain variance between your finished arrows with nothing screwed into the tips. Unless you weigh each vane, nock, insert, use exacting ammounts of glue and then match the heavier components with the lighter shafts and vise versa it isn't uncommon to see arrows that differ as much as 15 grains or more in a dozen after they are all finished.