Abstract: A blast diffuser for a gun, comprising bore means having a surface defining a barrel through which a projectile may be discharged when the diffuser is attached, in use, to a gun barrel, the blast diffuser further comprising a primary chamber arranged around the outside of the bore means and a secondary chamber adjacent to an outer surface of the primary chamber, wherein a plurality of holes are arranged in the surface of the bore means to the primary chamber, and a plurality of holes are arranged in the outer surface of the primary chamber to allow passage of combustion gases from the primary many chamber to the secondary chamber, the secondary chamber further comprising an opening to allow the escape of combustion gases into the atmosphere.