Close arthur, but no cigar. It's 2 fps for each pound of increase in draw weight. BUT, this only holds true if you're able to shoot the same arrow. If shooting a properly spined arrow for 60# you'd probably have to shoot a proportionately stiffer spined and heavier arrow at 70#. So, keeping arrow weight proportional to draw weight there isn't much difference between 60# and 70# in speed.