Grip frame, trigger housing and pistol grip are three separate parts. Grip frame and pistol grip would only count as one part if you were to use a one piece polymer grip frame.
Example with metal grip frame; trigger housing, hammer, trigger, sear, cocking handle, bolt carrier, and muzzle device to make it legal- so 7 US parts for 922r.
Example with metal grip frame; trigger housing, hammer, trigger, sear, cocking handle, bolt carrier, and muzzle device to make it legal- so 7 US parts for 922r.