I believe you are in correct on your last point. The renewed law only says "must be detectable." So the metal can be removable in this law. His amendment was

I believe you are in correct on your last point. The renewed law only says "must be detectable." So the metal can be removable in this law. His amendment was to force a permanent piece of metal. That worries us because even if the "full firearm" (assembled) might contain metal, the part that contains the serial numbers could no longer be made of polymer (this piece is technically considered the "firearm" for registration in NY, CT, and most likely CA).