As far as I know, there is no real way for the government to know what firearms a person has.some cities (and states) require all firearms to be registered, most dont. This is why I take any discussion about firearms in the US with a hefty grain of salt. Any numbers used in said discussion are guesses at best, more typically skewed towards whatever point the narrator is trying to make. I'm not necessarily against registration of firearms, nor do I think it would be a bad thing with current federal government. Where the fed is heading (witness current hard trend towards socialism) on the other hand, no way do I want those nuts knowing what I have.