If you want accurate u should start looming for a good barrel. Options are plentiful. I might have one for you. If you want cheap then You can scour the various forum classifieds and build a sub $600 gun.
Can u help me with a list i want to have a list of these parts so i can begin looking for the cheapest parts
This is the list or schematic that I use when ordering parts.
http://www.brownells.com/.aspx/pid=0/sid=814/schematicsdetail/Upper-Receiver-Barrel-Assembly
Here is the page with all the individual links to each different schematic...
http://www.brownells.com/.aspx/mid=114/schematics/DPMS-Panther-Arms-