Detectives Nemorin and Andrews Anti-Gun Trafficking Act of 2003

Detectives Nemorin and Andrews Anti-Gun Trafficking Act of 2003 - Amends the Brady Handgun Violence Prevention Act to prohibit the sale, transfer, or barter of two or more firearms, at least two of which are handguns, semiautomatic assault weapons, short-barreled shotguns, short-barreled rifles, or machine-guns, where at least one of the firearms: (1) is stolen or has had the importer's or manufacturer's serial number removed, obliterated, or altered; or (2) is offered by the person for sale, transfer, or barter to another person who is prohibited from owning a firearm, is under age 18, is in a school zone, or has travelled from another State and attempts to acquire the firearm in violation of law.

Amends the 21st Century Department of Justice Appropriations Authorization Act to: (1) direct that illegal gun trafficking be addressed as part of Project Safe Neighborhoods; and (2) extend through FY 2004 the authorization for hiring additional Assistant U.S. Attorneys.

Requires the Attorney General to report to Congress on traced firearms used in crimes, the Federal licensees who had more than 50 firearms traced to them in a year, and on prosecutions for individual firarms transaction offenses.

Directs the Federal Bureau of Investigation to: (1) make available to the Bureau of Alcohol, Tobacco, Firearms, and Explosives the National Crime Information Center Gun File to complete a crime gun trace; and (2) allow all Federal firarms licensees enrolled in the National Instant Criminal Background Check System to search the File with respect to any firearm the licensee receives from any person not licensed.

Sets forth additional penalties for possession, sale, or use of a stolen firearm (regardless of whether the person was aware that it was stolen) or a firearm with an obliterated serial number in the commission of a crime punishable by inprisonment for more than one year or a crime of violence.