YOu have probably missed the boat on building one now unless you want to spend hours stalking The Fal Files marketplace and Gunbroker etc for a QUALITY set of parts (they use to be plentiful but a quality set is much harder to come buy), then you need to get a receiver and probably have someone who has done it before to be around with the right tools and know how to look over your shoulder. Stalking a complete rifle on Gunbroker or another similar website or Fal Files M/Place is probably your best bet.