This actually works!!! Only for the Crossman c11 airsoft gun though. When the C02, as well as the BB is shot through the barrel the excess gas is absorbed in the silencer reducing the sound and making it sound much cooler.
Spray paint (any color)
Toilet Paper Roll
4'' Long hollow plastic or metal tube (must be able to fit snug into the neck of the bottle)
13/64'' drill bit
5/8'' drill bit
Small skiny object like a pen cartridge or a dowel