300 whisper. Its a necked up 223 rem cartridge, (or 221 fireball). I shoot 150 grain nosler ballistic tips that expand nice under lower velocity. I have buddy that loads mine to 2200 feet per second. I think without going and looking for the loading info its around 16.5 grains of H110 powder. Same ballistics about as a 30-30 out to 150 yards but ,,,,,now the good part,,,,,almost zero recoil and very little noise. Loaded with 220 sierra matchkings and subsonic 1000 feet per second, you get a deadly accurate load that makes as much noise as a 22 short. I use it for head shooting suburban deer. One shot and they fall down. A guy raking his leaves 200 yards away would not hear the shot. I do shoot out of tree stands.