I take it then that they 'somehow' know who bought what firearm which is basically registration and the next step prior to confiscation. Had you not had that unfortunate boating accident of course...
My guess is that when it comes time for the government to confiscate weapons, they will "find" a weapon on your property that suits them for the arrest. When they hit the first batch of owners and find nothing, they will change tactics. Fast-n-Furious, Waco, and Ruby Ridge indicate that when it comes to arresting people for firearms violations, there are no limits to what the Feds will do.
IIRC, Ruby Ridge was caused when a federal agent talked a man into sawing off the barrel of a shotgun for money.