1. Do not deal with someone who is wiling to break federal law by shipping to anyone but an FFL. You can't trust a cheater.
2. If you spending more for a gun than you are willing to throw away, research and choose a reputable escrow company to hold the funds until you receive and are satisfied with your purchase.
Kuleck/McKee 'AR-15 Assembly Guide' details a procedure for the assembled upper. Sounds like a check for proper lockup.
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