Shooting a target at 40 yds in your back yard and shooting at a deer at 40 yrds is quite different. You have to take the adrenaline factor into consideration. Not to mention, the deer's reaction to the release of the arrow. I saw something very interesting on the Dream Season last night. The participants ran a sprint before shooting at a target. By doing so, they simulated the adrenaline rush you get frombeing in the moment of shooting a deer. Try it and see how well you group at 40yds. It may or may not make a difference.