Straight from BATF:
"Neither the transfer of a repaired firearm nor the transfer of a replacement firearm would be subject to the requirements of the Brady law.
Furthermore, the regulations provide that a Form 4473 is not required to cover these transactions. However, the licensee’s permanent acquisition and disposition records should reflect the return of the firearm or the transfer of a replacement firearm."
http://www.atf.gov/firearms/faq/brad...epair-transfer