Ok so I received a AR pistol for a customer today from Radical Firearms. They built the pistol on a stripped Aero lower (Aero's complete roll mark, serial, and model info). The aero lower is the same one that you would get if you bought a stripped lower straight from them. Radical Firearms then engraved "built by Radical Firearms" on the lower. So my question is when entering into the book and putting the info on the 4473 would you put Aero or Radical Firearms? I would THINK you'd put Radical Firearms, then the serial and model that Aero engraved. Would this be correct?

The opposite side of the lower has the Aero roll mark, info and serial

Yes, you'd use Radical Firearms, as they took an Aero lower and turned it into a handgun. They must be a very small Type 07, though, if they couldn't afford to order enough lowers and get a marking variance to get Aero to put their rollmark on them, instead. Hell, there are shops out there who will/would do it for as few as 100 lowers.

That was my thought as well and odd that they didn't. I know this customer bought this about 2 months ago, so I'm wondering if they have been waiting on a variance and finally said screw it and started building and sending them. Hell a 07 local to me does markings for other 07 by just doing them 25 at a time. Getting some done with my logo and their manufacture info being I'm only a 01.