"Cylindrical barrel-mounted attachment; reduces speed of propellent gasses, resulting in an overall reduction of volume for each shot fired."
Armat A7 Sound Suppressor description (from Aliens: Colonial Marines - Arsenal Upgrades - M4A3 Service Pistol - Armat A7 Sound Suppressor)
The A7 Sound Suppressor is a cylindrical barrel-mounted sound suppressor manufactured by Armat Battlefield Systems for the M4A3 Service Pistol.


The A7 Sound Suppressor reduce the noise signature of each shot fired by allowing the rapidly expanding gases from the firing of the cartridge to be decelerated and cooled through a series of hollow chambers.