How Do Moderators Work?

Moderators are instruments designed for reducing the sound signature of a gunshot with the emphasis on reducing the risk of hearing loss.

As a shot is fired the precursor wave is the first to enter the moderator, followed by the projectile, then finally the blast wave, the main cause of hearing loss in shooters.

The recoil is generated by the combusting propellant, applying pressure to the rear of the projectile to gain the velocity required. As the projectile leaves the barrel it then passes into the blast baffle (Static Valve) which is one of the first components to come into operation.

The Blast Baffle serves three different purposes:

1. It is designed to help strip the high pressure gases away from the projectile (which can influence its flight) leading to accuracy issues.

2. The projectile partially seals the entrance to the blast baffle for a very short period of time (measured in milliseconds) allowing the blast wave/ gases to move rearward down inside the expansion chamber. This gives the projectile time to exit the moderator without the influence of the high pressure gas.

3. The blast baffle also acts as the muzzle brake which almost simultaneously occurs as the projectile enters into the blast baffle. It is the high pressure of the blast wave acting in conjunction with the specific weight of the projectile which gives the felt recoil. This pressure wave is then transformed to work in the opposite direction and apply forward force onto the face of the baffle which pushes the firearm away from the shooter thus reducing the felt recoil.

As the projectile moves into the forward section of the moderator it enters the baffle stack which has two functions:

1. The baffle stack helps to strip and deflect much of the precursor wave away from the path of the projectile.

2. As the projectile exits the moderator the blast wave (which is moving at approximately 2-3 times the speed of the projectile) is temporarily redirected to the filling of the rear expansion chamber. As the gas starts to flow into the forward section of the moderator the blast wave is met with the baffle stack which then helps the gas to further expand and cool which dramatically reduces the energy in the gas and so reduces the sound pressure level.