I am currently shooting a bear compound (2010 model 'lights out') with a 28 inch draw length set at 63 pounds. I don't know my exact arrow speed, but lets say it is around 280 fps. What is the ballpark increase in speed I would get by cranking it up to 70 pounds?
It's not going to affect it enough to be worth it. If I was you I would just shoot at the poundage I'm comfy at.
Check out backcountry archery calculator (google it). You can input your bow and arrow info and it will calculate you FPS and KE.
The whole problem is you will need new arrows. You will not be able to use the same arrows unless they are already WAY overspined. Typically the same arrow in a stiffer size will be heavier. This will eat up potential speed gains. Without specific details,it is impossible to predict how much,if any speed you will gain. However,you will gain energy in the form of ke and momentum,as long as the arrows are tuned and spined properly. Don't worry about speed. Shoot what is most comfortable and build the arrow accordingly.
