Audio forensics is the one issue in the field of forensic science to investigate the crime committed by using firearms. The gun blast gives us important information of its caliber leading to identifying the firearm used by the criminal in the crime scene. It can be recorded by an audio-recorder under various conditions. In recording process, the gunshot blast is affected by many factors, including the type and the caliber of firearm, the location of shooter, wind speed, temperature, sound reflection and reverberation, the type and the quality of bullet, the direction of the firearm, the shooting position, and the orientation or the location of the sound recorder. Those features make the firearm identification from the gunshot blast more difficult.