November 21 2012 – Silent but deadly: US Special forces seek quiet, subsonic bullets
CNN reports that the Pentagon’s special forces want to be sneakier with slower, quieter bullets which makes it hard to be sneaky about what they’re shooting. Most bullets that travel 1,100 feet per second at sea level make small sonic booms when flying through the air, which to our ears sound like a loud, distinct “crack!”. The quieter bullets would travel slowly enough not to break the sound barrier. However these subsonic bullets do pose a greater risk of jamming.
The Sound of Gun Fire from Downrange: 380 Yard Shots. The super sonic “crack” of the bullet is heard first, then the sound of bullet striking the target, then the low frequency muzzle blast and the reverberation. Hollywood never gets this right:
Mythbusters Sonic Boom Sound Off – Sonic Booms break glass?