If you had two arrows one 27" and one 29" and you were bare shafting with 125 grain points, and the 29" arrow shot the best how many grains of point weight would you need to increase get the 27" to bare shaft the same as the 29"? Brokenwing
It's not quite that easy, but the short answer is a LOT. That's a pretty big difference.
I have some set-ups that I can shoot both 125 and 160 grain points, I only need to take about 1/4 inch off the arrow to shoot the 160's.
Very roughly....60-70 grains. But as Slowbow said-it isn't always that easy. My limited experience with carbon shafts has shown that they don't always behave the way I would accurately predict on wood.... and even woodies can throw an occassional curve.
With carbons, especially the thinner diameter, thicker walled H.I.T Axis, or Bemans, it's waaay easier to tune by nibbling length off the nock end if you have to. I've added as much as 100 extra grains and had 'em bareshaft close at 20 yards...