Correct, of course you must be able to show its 50yrs old or on the list for most dealers to be able to show it in the BB if necessary.
https://www.atf.gov/firearms/curios-relics"ATF has recognized only complete, assembled firearms as curios or relics. ATFs classification of surplus military firearms as curios or relics has extended only to those firearms in their original military configuration.
Frames or receivers of curios or relics are not generally recognized as curios or relics."https://www.atf.gov/resource-center/docs/p-5300-11-firearms-curios-or-relics-listpdf-0/download 
