I have had some silencer adaptors made for the Air Arms S4** range, i know that silencer adaptors are nothing new but mine are a bit diffrent.
My adaptors come with a in built still air cone.
This helps to stablilise the pellet after leaving the end of the barrel, but this also removes a large amount of air befor entering the silencer. This has had very good results so far, the accuracy has improved from 30 yards plus and i have also been told that it has made some silencers quieter.
These have been made on a CNC machine out of T5 aluminium and have been hard anodised black.
There are some pics in my link posted in my signature. If any one would like one of these then please contact me.
http://www.picturetrail.com/gallery/view?p=6&uid=9453841&