The instant that a cop runs the serial number of your gun, it becomes a “crime gun.” So, if you get pulled over, tell the cop you’ve got your (totally legal) gun with you, and he takes it and radios a trace request, it’s a “crime gun.”
Of course, reality has no meaning in this situation. You didn’t commit any crime, and the gun was not connected to a crime. But the local political hacks can rend their garments and gnash their teeth over the existance of another “crime gun” in their jurisdiction.
Hence the Tiahrt amendment.
I'd be arrested and charged with a felony. I live in Illinois.