Subsonic ammunition is designed to operate at velocities below the speed of sound at standard atmospheric conditions at approximately 1,116 fps or Mach 1, which prevents the supersonic shockwave, or “crack,” of the projectile when the round is discharged. When used with a sound suppressor, subsonic ammunition is effective at reducing the acoustic intensity of the muzzle report by modulating the speed and pressure of the propellant gas released from the muzzle.
