I'm pretty sure the newer-ish sonix uses tabs, but a picture would help confirm. Is it this one?:
Expansion chambers are only useful if you are going to use c02, otherwise its just more o-rings you have to replace. If you are using c02, unless you're playing in colder weather its still debatable if they help for a mechanical gun, although I guess they are slightly cheaper than some options.
IMO no bolt is really going to do that much to quiet the gun, for the money you'd be better off looking for a barrel with lots of porting or a regulator instead of the expansion chamber to reduce the pressure.