Originally Posted by gwalchmai
I'm not following you. Your FFL reports your purchases to "the feds"?
Without getting into specifics, identifiers for any firearm encountered by a law enforcement agency can be submitted for a "trace". This will find and include all transfers of the firearm through any FFL back to the earliest.
In the case of a very old firearm that was never sold through a dealer and never changed hands except through a private sale, the firearm would not be traceable.
If the government requires all sales to go through an FFL then all firearms will eventually be traceable to the seller and buyer.