I'd check with the States involved. For example, a new law (last year) in WA State does NOT permit me to loan/give/sell a firearm to another without a background check. No legal test cases to challenge this one yet... but, a PITA tossed at us (thanks to Bloomberg and his minions). Beyond that... just be in compliance with any applicable SBR regulations IF that applies.
I don't know of anything w/I the 3-gun entities' rules... but, might be worth asking whether 80% lowered equipment is sanctioned by them. "?"