Effects on Noise Reduction and Muzzle Velocity by Conical Walls in a Suppressor for 9-mm Pistol Effects on Noise Reduction and Muzzle Velocity by Conical Walls in a Suppressor for 9-mm Pistol

Abstract

A suppressor is the device used to reduce the acoustic intensity of a firearm report. It is normally expensive and only available in governmental agencies. The objective of this research is to study and develop a suppressor made of affordable materials, which can reduce the sound intensity to the degree equivalent to traffic noise (80-90 decibels). The suppressor, made of aluminum with the diameter of 34 millimeters and the length of 254 millimeters, was attached to the muzzle of a 9-mm pistol, using 130-grain subsonic bullets (with a speed below 330 meters per second). The testing was set out by firing the suppressed pistol into the standard target at a distance of 10 meters, 3 rounds at a time. The sound intensity was measured by a standard sound level meter IEC61672 class 2 at a distance of 5 meters from the sound source. The result showed that the average noise of the unsuppressed pistol was 106.9 decibels with an average muzzle velocity of 296.6 meters per second, compared to the result from the suppressed pistol with maximum of 7 conical walls, the average sound intensity was maximally reduced to 90.8 decibels and the average muzzle velocity was 295.5 meters per second, accounting for 15 percent and 0.37 percent respectively. This study showed that there are two factors that affected noise reduction. First, it is the reduction of gas pressure emitted from the cartridge which was trapped in the inner and outer space of the conical walls. Second, the gas was drained radially and infiltrated the space, causing the delay and pressure breakdown before being reflected into the atmosphere. These factors lowered the relative pressure comparing to atmospheric pressure and decreased the sound volume as well as the muzzle velocity. However, the lower muzzle velocity produced greater accuracy at a distance of 10 meters and reduced recoil, not to mention the suppressor’s weight which also reduced muzzle rise. According to this research, the suppressor, made of domestic inexpensive materials, could reduce the noise of the firearm report and at least 80 percent of shot groups hit the targets.