i use a Gemtech HALO silencer on my VFC 416 with a 10" (250mm) barrel and it really cuts down on the report from the muzzle. most people who have played along side me are impressed of how quiet my gun is. granted a lot of that comes down to the parts you use in your gearbox, but there is quite the difference in loudness when i take the silencer off. during a game this past week, i ran the first half with my can on and the rest of the afternoon with it off. the report from my muzzle was noticeably louder than even the GBBRs, and i could be distinguished from everybody else in the thick bush just by the muzzle report. the Gemtech doesn't use foam like most other cans out there, instead it uses a heavily packed wool like material. what ever that stuff is, it works really well.
Weapons Technician / Gunsmith
Don't look at me, I don't know, lol ¯\(°_o)/¯.