Q) I have an Air Ranger FAC 40ft/lb with an MTC Viper 6-24 x 56 by its side. It is a winning combination, but noisy. Daystate told me to use a sound moderator and said it could make a new shroud, less the baffles, making it 5in shorter overall. This would allow me to add a sound moderator to maintain the original length. I bought an Air Stream 111, as advised, and this has reduced the noise by a quarter, but the rifle still makes a loud crack. Are there any sound moderators that could reduce the noise even more?
A) As your air rifl e is fi ring a pellet that is producing a muzzle energy of around 40ft/lb, the pellet velocity at the muzzle must be in excess of the speed of sound, ie 1,115fps at sea level. This supersonic pellet is producing the loud crack that you are experiencing. The Air Stream 111 sound moderator has eliminated the muzzle report caused by the compressed air, which is propelling the pellet, hitting the air as the pellet exits the muzzle. The supersonic speed of the pellet is producing the loud crack. The only way you can eliminate this crack is to reduce the velocity of the pellet to subsonic. I would not be concerned about the crack, which, though very audible to you, would be completely inaudible to any live quarry that you hit. The pellet would hit it before the crack was heard. However, if you miss, the quarry will hear the crack as you do.