Six if you thread the muzzle for a brake or FH. The five easy parts are hammer, trigger and disconnector (Tapco G2 or other set), pistol grip (Magpul or others), and gas piston (Century or others.) If you want Magpul handguards, that's one part.
A USA mag counts as three parts (body, follower, and floorplate.) USA floorplates for commie mags can be found easy enough, and cheap.