I' ve always been a firm believer that if you can keep ALL of your arrows in a pie plate, no matter what the range, that was your effective range you could shoot at. I do however, believe there is a point that is beyond logic to shoot at. Like you, I believe that is 40 yards. Beyond that, there' s just too many variables. Like the animal moving, or, having enough energy left in the arrow to completely pass thru. It does no good to be able to hit a 2" circle at 80 yards, if it' s going to only penetrate an inch or so due to loss of energy.