Thanks for the reply, is damage to the bow the main reason to make sure that a arrow is too weak in the spine? I am more than likely going to turn the bow down around 70lbs no matter what, but i believe that these maxum 2315s I just bought are around 320 grains....if thats what the name implies...these are called Maxum Quattro 320, and are size 2315, but the first ones i was shooting were Maxum Quattro 420, size 2215....does this make any sense??