"Why punish the millions of law abiding citizens?"

What possible punishment could it be to a law abiding citizen to have a record of the ballistic characteristics of their guns in the hands of the authorities? It could even help in restoring a gun to the owner if it had been stolen.

I suppose, if the gun had been stolen and was used in a crime, and the owner hadn't bothered to report it, the owner might have a problem - but I would be extremely suspicious of anyone who failed to report a stolen gun. In fact I would rather assume that that is some kind of offence already. A rather serious offence. If a stolen gun were used in a crime the owner who hadn't reported it missing wpou;d effectively be some kind of accessory before the fact.