Re: It will identify the weapon
As I pointed out, this idea has only one plausible function: to establish a working database of those who go in and buy new guns and take them home for legitimate purposes. Legal, non-criminal gunowners. Everyone else can easily circumvent it in the many ways mentioned here, even assuming you don't bring a gun in from Mexico or Canada.
And why legitimate gunowners should be targeted like this is an exercise left for the reader.