He is talking about grains per pound, and @ 6 grains per pound the arrow will weigh differently at 60#'s and 50 #'s......

6x60 = 360
6x50 = 300

To shoot a 360 grain arrow out of both a 60 and 50 pound bow wouldn't be comparing the same thing. The 60# bow is gonna shoot that arrow about......25 fps or so faster than the 50, so it wouldn't be an even playing field.

Again, a heavier arrow will retain it's speed and momentum longer than a light arrow. At least, I THINK that's what TFOX is getting at...eh buddy?