Requires new rules that force most U.S.-made firearms to carry a second serial number that is placed inside the receiver or only visible in infrared light, expands the legal definitions of "receiver" and "unfinished frame or receiver," and directs the Attorney General to write implementing regulations on background-check record retention and mandatory dealer inventory checks. It also amends multiple prior appropriations provisions to prohibit using federal funds to impose any tax or fee tied to implementing the instant background-check process.

Sets firm deadlines for agency rulemaking (12 months for the internal/IR serial-number requirement; 180 days for record-retention and inventory rules), creates new compliance duties for manufacturers and licensed dealers, and changes criminal- and regulatory-related definitions that affect how firearms and partially finished parts are treated under federal law.