I was having problem taking of the Barrel Nut (Too tight). With help from one of the member here "Karnage", I have it done. Now I want to post picture of how I do it to help whoever having the same problem.
First, I stick a screw driver where the front body pin goes it to give support for the upper receiver to prevent breaking it.
Then flip it over and let it stand on the receiver, put a flat head screw driver on the tap of the delta ring and use a hammer to tap it (Use a little force)!!
After a couple of tap, if finally come lose...
Now, the question remain is if this is the bare minimal I can take it down to, or I can take out the black piece from the upper receiver?
Thanks