That is a Whisper Fusion. The velocity stamp is mainly for marketing purposes, and can only be achieved with the lightest pellets (which won't shoot worth a damn at that high velocity). You will find that the rather harsh recoil will make the thing a steep, but in many respects a worthwhile learning curve to shoot well. Also, the 10 to 11 grain pellets will do better since they will shoot slower. Ideally, pellets should be kept to about 850 ft/s or a bit slower.