Muzzle blast

Muzzle flash is the visible light of a muzzle blast, which expels high temperature, high pressure gases from the muzzle of a firearm. The blast and flash are caused by the combustion products of the gunpowder, and any remaining unburned powder, mixing with the ambient air. The size and shape of the muzzle flash is dependent on the type of ammunition being used and the individual characteristics of firearm and any devices attached to the muzzle (such as a muzzle brake or flash suppressor).

The muzzle flash is often broken down into two components, an auditory component and a non-auditory component. The auditory component, the sound of the muzzle blast, is important because it can cause hearing loss or give away the gun's position, while the non-auditory component, the overpressure wave, can cause damage to items near the blast.

The sound of a gunshot may have two sources; the muzzle blast itself, and any sound produced by a transonic or supersonic projectile. Suppressors help to reduce the level of sound of a firearm, by providing a large area for the propellant gas to expand and cool before release.

The overpressure wave from the muzzle blast of a firearm can contain a significant amount of energy because it travels at an extremely high velocity. Residual pressures at the muzzle can be a significant fraction of the peak chamber pressure, especially when slow burning powders or short barrels are used. This energy can also be harnessed by a muzzle brake to reduce the recoil of the firearm, or by a muzzle booster to provide energy to operate the action.

Muzzle blasts can easily exceed sound pressure levels of 140 decibels, which can cause permanent hearing loss even with brief and infrequent exposure. With big guns such as artillery, that danger can extend outwards a significant distance from the muzzle.

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