The picture of your gun does not show.
I will assume that it's a TM-style barrel nut, looking like this:
Also, that second "what it should be like" is not actually what it should be. Most airsoft that have the dented ring will use a setup similar to real steel, where the dented ring is part of the nut, and the delta ring/spring are held in place with a large C-clip:
In any case, you can probably still install a RAS (replaces your stock plastic handguards) or free-float, as most free-float setups use a special barrel nut that replaces the delta ring.