On the Whisper the scope is above the barrel, so there is a couple of inches (or more) between the barrel, and the center of the scope. For me, to get a 25 yard zero, put an aiming spot on the target, about 1 to 1/2 inches above the center of the bull, and zero gun to hit center, while aiming at the spotl If your scope adjustments were not centered, you may have a couple of turns to bring your impact point to center. Then shoot at longer range...you will be real close at 25 yards. Also, do you have a parallax adjustable scope? If not, then head placement is very important. Move your head, watch the cross hairs move too!
Douglas George