imported post
Despite what TV crime dramas would have you believe, there is very little gun registration in the U.S., and tracing a gun is almost impossible unless it is in the hands of someone who purchased it new from a dealer and has not moved.
These states require handgun registration: CT, HI, IL (partial, by city ordinance), MD, MA, MI, NV (Clark County only), NJ, NY, and NC (Durham County only).
In all others, there is no registration, although Pennsylvania has a "purchase registry" that only covers purchases from dealers (private sales are legal).