Jim/Hugh,
When I wrote the “Building an 80% Firearm” series for SB I briefly touched on how to keep a similar low profile. I would add the following : Face-to-face (FTF) using cash is certainly king and the most likely to allow anonymity. Buying the the remaining parts for an 80% or conventional build at a gun show or using BackPage or Armslist is reasonably easy. Buying your 80% lower the same way is also best if available but the finding 80% lowers through any of those three sources is still sparse. Many gun shows do not have an 80% vendor. However here are two ways to get most if not all of the desired OpSec when buying your 80% lower. I have done both and the FTF method is more secure. I would always wear non-descript clothing complete with hat and glasses for any transactions and park a little ways away as many retail sources or parking lots where you meet a private seller have some type of camera surveillance.
FTF (face-to-face method) If a FTF at a gun show/BackPage/Armslist is not a possibility, then find an 80% manufacturer or distributor that you can drive to. I listed 17 manufacturers of AR lowers in my article and they are spread out in the U.S. Many of them will let you know if they have a distributor in your area. If their distributor stocks or will do a prepaid cash order for you, just pay cash and call it a day with your OpSec preserved. If you have to drive very far combine it with a vacation or day trip for further OpSec. We took the kids to Disneyland and stopped by 80Percent Arms in Santa Ana-literally 5 miles down Harbor Blvd. from Disneyland – and made the retail cash purchase. I saw two vehicles in their parking lot with their license plats all but invisible as well.
Low profile mail order I contacted Blitzkreig Tactical in San Diego and after conferring with the owner, they agreed to allow me to do a prepaid anonymous money order as long as I clearly spelled out what I was ordering and where it was to ship. I squared away the details with their CS rep over the phone and sent out the order via snail-mail. I work for a medium-size company where the receiving clerk is also a good friend and fellow prepper. I had it sent to the company address to Att: Receiving and he alerted me when it arrived. Any potential for a paper trail is very thin since 250 people work here. All he will say is that the box arrived but was gone from the shelf the next day. I’m sure you can think of an equally creative way to keep things on the very down-low.
Hope this helps, – Wontogo